Boris Johnson has said he will "keep fudging" on whether or not he will stand to be an MP in 2015, to the frustration of an influential committee of Tory backbenchers.
Speculation has been mounting on whether the London mayor will return to parliament - and potentially succeed Cameron as leader of the Tories.
Appearing on Pienaar's Politics on Radio Five Live, Johnson was asked whether he would "keep fudging" on this issue and he replied "yes".
Boris Johnson has still not confirmed he will stand for parliament in 2015, as is expected
It has been reported Johnson will announce he will stand for a safe Tory seat in 2015 but pledge not to take a ministerial post while he serves out the remainder of his term as mayor, which ends in May 2016.
But backbench MPs have criticised his failure to confirm his plans.
Charles Walker, vice-chair of the 1922 Committee of Conservative MPs, told The Observer: "Boris needs to decide what he is doing. He needs to be decisive.
"Undoubtedly, he would be a great addition to parliament, but he needs to get on and decide what he is doing if he is to be taken seriously."
Many potential seats have been suggested for Johnson, including North West Hampshire, where Sir George Young has said he will stand down at the next election.
Boris Johnson's Funniest Moments
Tennis - AEGON Championships 2013 - Day Seven - The Queen's Club(01 of46)
Boris Johnson (centre) takes part in a celebrity tennis match in aid of the Royal Marsden Hospital at The Queen's Club, London. (credit:PA)
Boris visits Lloyd's of London(02 of46)
London Mayor Boris Johnson gives a speech during a visit to Lloyd's of London as part of his engagement with the City, London. (credit:PA)
Johnson launches 2020 Vision plan for London(03 of46)
London Mayor Boris Johnson launches his 2020 Vision for London at City Hall, London. (credit:PA)
American Football - NFL International Series - New England Patriots v St Louis Rams - Wembley Stadium(04 of46)
London mayor Boris Johnson before the NFL International Series match at Wembley Stadium, London. (credit:PA)
Tennis - AEGON Championships 2013 - Day Seven - The Queen's Club(05 of46)
Boris Johnson (centre) takes part in a celebrity tennis match in aid of the Royal Marsden Hospital at The Queen's Club, London. (credit:PA)
Will & Jayden Smith with Boris johnson(06 of46)
Will Smith (right) at City Hall in London join London's Mayor, Boris Johnson, to celebrate the achievements of the Mayor's Leadership Clubs that were launched in schools across the capital earlier this year. (credit:PA)
Gu 10th birthday(07 of46)
EDITORIAL USE ONLYMayor of London Boris Johnson makes a Gu chocolate souffle with head chef Fred Ponnavoy in the Gu development kitchen, in Walthamstow, to celebrate the London-based premium dessert companys 10th birthday. (credit:PA)
Rugby League - Martin Offiah and Boris Johnson Photocall - Tower Bridge(08 of46)
London Mayor Boris Johnson takes a 'Big Hit' for London from RLWC2013 ambassador Martin Offiah during a photocall at Tower Bridge, London. (credit:PA)
Third runaway protest(09 of46)
Mayor of London Boris Johnson poses with a protester dressed as a rabbit at a rally in Barnes, London, against the expansion of Heathrow Airport. (credit:PA)
Boris visits Brasserie Blanc(10 of46)
Mayor of London Boris Johnson meets workers at one of Raymond Blanc's Brasserie Blanc restaurants in the City of London where he urged the capital's food and hospitality firms to take on more young people as apprentices. (credit:PA)
Apprenticeships(11 of46)
Mayor of London Boris Johnson at Crossrail Tunnelling Academy in Ilford Essex, where he met apprentices. (credit:PA)
Mayor of London Police and Crime Plan launch(12 of46)
London Mayor Boris Johnson arrives to join Metropoiltan Police Commissioner Bernard Hogan-Howe and members of the Dalston Safer Neighbourhood scheme in Hackney, east London on their local beat where they launched the Mayor's Police and Crime Plan. (credit:PA)
Boris Johnson visits Ealing Studios(13 of46)
Mayor of London Boris Johnson with actor Matt Cross (left) and Dawson James as he visits The Imaginarium at Ealing Studios in West London, where he took part in a Performance Capture session. (credit:PA)
Boris visits Brasserie Blanc(14 of46)
Mayor of London Boris Johnson joins chef Raymond Blanc at one of his Brasserie Blanc restaurants in the City of London where he urged the capital's food and hospitality firms to take on more young people as apprentices. (credit:PA)
Boris Johnson / Tory Conference(15 of46)
Boris Johnson MP takes a break from the Tory Party Conference in Bournemouth. 13/11/2004 Boris Johnson who was Saturday November 13 2004, sacked from the Conservative frontbench amid fresh allegations about his private life, a spokesman for Tory leader Michael Howard said. (credit:PA)
Boris visits youth club(16 of46)
Mayor of London Boris Johnson playing tennis during a visit to Crown and Manor Youth Club in north London, a 100-year-old youth club that has helped 10,000 boys. (credit:PA)
Boris Johnson visits India - Day 5(17 of46)
Mayor of London Boris Johnson plays the 'Ball Game' with former rugby player Lawrence Dellaglio and local children involved in the Magic Bus Project in Mumbai today. (credit:PA)
Boris Johnson visits India - Day 6(18 of46)
London mayor Boris Johnson at the Gate of India in Mumbai, after meeting business leaders at the Bombay Stock Exchange, as part of a week long tour of India where he is trying to persuade Indian businesses to invest in London. (credit:PA)
Boris Johnson visits India - Day 5(19 of46)
Mayor of London Boris Johnson plays the 'Ball Game' with former rugby player Lawrence Dellaglio and local children involved in the Magic Bus Project in Mumbai today. (credit:PA)
Boris Johnson visits India - Day 5(20 of46)
Mayor of London Boris Johnson plays the 'Ball Game' with former rugby player Lawrence Dellaglio and local children involved in the Magic Bus Project in Mumbai today. (credit:PA)
Boris Johnson visits India - Day 4(21 of46)
England cricketers Stuart Broad (left), James Anderson (2nd left), Kevin Pietersen (2nd right) and Matt Prior (right) pose for a photograph with Mayor of London Boris Johnson at a reception hosted by the Mayor in Mumbai, India. (credit:PA)
Day 2 - Paralympic Torch Relay(22 of46)
Mayor of London Boris Johnson (left) with Prime Minister David Cameron during the lighting of the Paralympic Cauldron in Trafalgar Square, central London. (credit:PA)
School playing fields(23 of46)
London Mayor Boris Johnson speaks about protection of school playing fields at the Sea Life Aquarium, London. (credit:PA)
Poppy Appeal(24 of46)
Mayor of London Boris Johnson on board the HMS Severn ship on South Quay to launch the largest ever London poppy day appeal. (credit:PA)
Conservative Party Conference 2012(25 of46)
Mayor of London Boris Johnson addresses the Conservative Party conference at the International Convention Centre in Birmingham. (credit:PA)
Day 2 - Paralympic Torch Relay(26 of46)
Mayor of London Boris Johnson (left) with Prime Minister David Cameron during the lighting of the Paralympic Cauldron in Trafalgar Square, central London. (credit:PA)
Day 2 - Paralympic Torch Relay(27 of46)
Mayor of London Boris Johnson (left) with Prime Minister David Cameron during the lighting of the Paralympic Cauldron in Trafalgar Square, central London. (credit:PA)
Mayor Boris Johnson aviation timetable(28 of46)
Boris Johnson, the Mayor of London, during his speech at London City Hall, where he told the Government to speed up aviation capacity in the south east of the country or risk economic stagnation for the whole of the UK. (credit:PA)
Olympics - London 2012 - Opening of 124th IOC Session - Royal Opera House(29 of46)
London Mayor Boris Johnson at the Opening of IOC Session at the Royal Opera House, London. (credit:PA)
London Olympic Games - Day 16(30 of46)
Mayor Boris Johnson (left) and Arnold Schwarzenegger take a ride on the Emirates cable car from Greenwich to the ExCeL in Docklands, after watching the Olympic basketball in Greenwich. (credit:PA)
London 2012 Ticketshare scheme(31 of46)
London Mayor Boris Johnson plays basketball with pupils from Chiswick Community School in west London where he and London 2012 Chairman Lord Coe told the school how many Olympic tickets they would receive through the London 2012 Ticketshare scheme. (credit:PA)
Paralympics - International Paralympic Day - Trafalgar Square(32 of46)
London Mayor Boris Johnson prepare to plays tennis during the International Paralympic Day in Trafalgar Square, London. (credit:PA)
Phone hacking claims(33 of46)
London Mayor Boris Johnson speaks at a press conference at City Hall in London, where he confirmed that Deputy Commissioner Tim Godwin would run Scotland Yard, following the resignation of Sir Paul Stephenson who resigned as Metropolitan Police Commissioner on Sunday night. (credit:PA)
Rhythm of London Busking Competition(34 of46)
Mayor of London Boris Johnson is handed a guitar by musician Newton Faulkner at London Bridge Station to highlight the Rhythm of London Busking Competition, London. (credit:PA)
Rhythm of London Busking Competition(35 of46)
Mayor of London Boris Johnson joins musician Newton Faulkner at London Bridge Station to highlight the Rhythm of London Busking Competition, London. (credit:PA)
Barbara Windsor joins Big Lunch initiative(36 of46)
Mayor Boris Johnson announces Barbara Windsor as his 'Street Party Champion' for the Big Lunch, during a visit to the Rocky Park Urban Growers project on the Teesdale and Hollybush estate in Bethnal Green, London. People all over the UK are being encouraged to take part in the Big Lunch initiative this June, an annual event in which people have lunch with their neighbours. (credit:PA)
Access All Areas photocall(37 of46)
London Mayor Boris Johnson (right) meets award winning rapper, Chipmunk at City Hall in London where he was speaking at Access All Areas, a music seminar for young people organised as part of the Mayor's Rhythm of London event. (credit:PA)
4th Plinth(38 of46)
London Mayor Boris Johnson with a sculpture of a blue cockeral as he unveils the next two commissions for the fourth plinth in Trafalgar Square, which includes the cockeral (pictured) by Katharina Fritsch and a boy on a rocking horse named Powerless Structures by Michael Elmgreen and Ingar Dragset. (credit:PA)
Story of London festival(39 of46)
London Mayor Boris Johnson takes part in a scientific experiment at the Royal Institution in central London to officially launch the Story of London festival. (credit:PA)
Conservative Party Annual Conference(40 of46)
Mayor of London Boris Johnson addresses the Annual Conservative Party Conference at the International Convention Centre, Birmingham. (credit:PA)
Story of London festival(41 of46)
London Mayor Boris Johnson takes part in a scientific experiment at the Royal Institution in central London to officially launch the Story of London festival. (credit:PA)
T-Mobile Big Dance 2010 launch(42 of46)
Mayor of London Boris Johnson takes to the stage to launch T-Mobile Big Dance 2010 at the London Palladium, London. (credit:PA)
Chinese New Year celebrations(43 of46)
Mayor of London Boris Johnson holds a Chinese dragon costume at a photocall in London's Chinatown district to promote the capital's Chinese New Year celebrations, which mark the start of the year of the Tiger on Sunday 21st February. (credit:PA)
Chinese New Year celebrations(44 of46)
Mayor of London Boris Johnson wears a Chinese dragon costume at a photocall in London's Chinatown district to promote the capital's Chinese New Year celebrations, which mark the start of the year of the Tiger on Sunday 21st February. (credit:PA)
BGC Annual Global Charity Day - London(45 of46)
Mayor of London Boris Johnson and the Cheeky Girls help out on the trading floor at the BGC Partner's 7th Annual Charity Trading Day, at Churchill Place in Canary Wharf, east London. (credit:PA)
Disturbances across the UK(46 of46)
London Mayor Boris Johnson holds a broom as he addresses members of the community outside Clapham Junction railway station following a night of disturbances across London and parts of the UK. (credit:PA)