David Cameron will attend the Leveson Inquiry into press standards if summoned to give evidence, Downing Street has said.
The revelation comes as three editors of broadsheet national newspapers are to face questioning at the official probe, ordered by the prime minister following the exposure of illegal phone hacking at the News of the World.
The Daily Telegraph's Tony Gallagher, Lionel Barber of the Financial Times and the Independent's Chris Blackhurst are expected to be asked about their papers' approaches to ethics, fact-checking and complaints.
Further testimony will come from former Daily Telegraph editor Will Lewis, who joined News International in September 2010, and Telegraph Media Group chief executive Murdoch MacLennan.
Responding to reports that Lord Justice Leveson is "99.9%" certain to call Mr Cameron for questioning under oath about his dealings with senior media executives and press baron Rupert Murdoch, a Number 10 spokeswoman said: "A request has not yet been received. If asked, the prime minister would of course attend."
Former PM Gordon Brown and Labour's current leader Ed Miliband are also expected to appear when the inquiry focuses on relations between the media and politicians, The Times said.
A Leveson Inquiry source told the newspaper the final decision on which politicians to invite had not yet been made but added: "I can't see how you can look at the relationship between the press and politicians without talking to top politicians, including the prime minister, the previous prime minister and the leader of the opposition."
The newspaper suggests Mr Cameron is likely to be called after the local elections in May. It is expected questioning will focus on his decision to employ Andy Coulson, the former editor of the defunct News of the World, who quit as Downing Street's director of communications amid continued pressure about phone hacking.
The inquiry on Monday heard from executives and senior reporters at The Sun, Britain's top-selling daily newspaper. Editor Dominic Mohan said the paper could be a "powerful force for good" through its campaigns, support for charities and ability to explain complicated stories in a clear way.
Mohan, a former showbusiness reporter who took on the editorship of The Sun in 2009, appealed for there to be a "level playing field" between the press and internet publications.