No 10 has said Chancellor George Osborne is "100% focused" on the economy amid allegations about his private life before he became an MP.
The claims, dating back nearly 20 years, were made in Australia by ex-escort agency boss Natalie Rowe, who had a child with a friend of the MP.
Ms Rowe also claimed her phone may have been hacked by the News of the World.
A spokesman for Mr Osborne has said there is "nothing new" in her claims, which have been repeatedly denied.
The News of the World published a photo of Mr Osborne and Ms Rowe on its front page in 2005, when the Conservatives were in opposition and Mr Osborne was running David Cameron's Conservative leadership campaign.
At the time, Mr Osborne said he had met Ms Rowe when he was 22 and she was the partner of a close friend of his who developed a serious drug problem.
But he strenuously denied any improper conduct himself.
In an interview with Australian broadcaster ABC, Ms Rowe repeated allegations first made in 2005 and also claimed police had told her that her name was on a list of phone numbers seized from private investigator Glenn Mulcaire, jailed for illegally intercepting voicemail messages in 2007.
The Metropolitan Police have not said whether her name had featured in their investigation into phone hacking allegations.
Asked about the allegations, a No 10 spokesman said it was "very clear to me that the chancellor is 100% focused on the UK economy".
A spokesman for Mr Osborne commented: "These are old allegations that were widely reported and denied years ago. There is nothing new in them."