Boris Johnson has made his fiercest attack yet on David Cameron, accusing him of overseeing an "economic catastrophe", just days before the Tory party conference.
The London mayor accused Cameron's government of giving "lamentable attention" to the issue of more airport capacity, pushing for a four-runway airport in the south east, rather than a third runway at Heathrow.
"The government programme to address the looming aviation capacity crunch in the UK is far too slow and I am hugely concerned that their intended timetable sets a course for economic catastrophe," he told a group of business leaders.
"This continued inertia is being fully exploited by our European rivals who already possess mega hub airports that they intend to use to erode our advantage."
Boris is strongly opposed to the construction of a third runway at Heathrow and has instead argued for a new airport to the east of the city in the Thames Estuary.
The London mayor, who has become notorious for outshining the prime minister at recent public events, previously accused Cameron of "pussyfooting" around the issue.
And last month Boris attacked the demotion of Justine Greening as "simply mad".
Thursday's comments come days before Johnson is due to give a keynote speech at the Tory party conference in Birmingham, where he is likely to continue to ride a wave of popularity from the successful Olympic Games.
He is also set to speak at a fringe meeting in Birmingham titled: "Boris Johnson's 2012. Re-elected and Olympotastic".
Cameron and Johnson reportedly held a "peace summit" at the prime minister's country retreat Chequers last week, in an attempt to defuse tensions between the two.
Johnson would not go into details about what he and David Cameron discussed when asked on Thursday, but did say: "I believe David Cameron is going to win the next general election.
"The Government are doing the right thing for the economy and are doing what the country needs them to do."
The London mayor has also seen a surge in popularity following the Olympic Games. An Ipsos Mori poll found 61% of people had a more positive view of Johnson following the sporting event compared with 43% for Cameron.
He managed to upstage his Oxford rival as they spoke to mark the end of the Games, leaving crowds chanting "Boris" at the parade finale.
Speculation over Johnson's political ambitions surfaced after last year's Tory party conference, when Jeremy Paxman asked the mayor whether he could lead the Conservative party during a bizarre Newsnight interview.
However Johnson turned the question into farce by suggesting the TV veteran should stand, with the Conservative mayor as his campaign manager.
“You’ve got the gravitas, you’ve got the name recognition, everybody knows that you’re probably quite Conservative, even though you sort of levitate over party policy," he said.