Mr Cameron was flown by private jet to Santorini on August 16 where he joined Mr Murdoch for drinks on his 184ft yacht, Rosehearty.

The Gulfstream IV belongs to public relations guru Matthew Freud who is married to Mr Murdoch's daughter, Elisabeth.

The Tories insisted Mr Cameron had done nothing wrong and that the flights had been fully declared in the Register of Members' Interests.

A spokeswoman for the Tory leader said: "Everything in connection to August 16 has been fully and properly declared."

Although Mr Cameron registered the fights last month, until now nothing had been made public about his visit to Mr Murdoch's yacht.

The disclosure is likely to add fresh fuel to the controversy surrounding shadow chancellor George Osborne's visit to the Russian billionaire Oleg Deripaska on his yacht off Corfu.

Mr Osborne has denied claims by the financier, Nat Rothschild, that he used the visit to try to solicit a £50,000 donation for Tory party funds, although he has admitted he was present when a possible donation by Mr Deripaska was discussed.

In the case of Mr Cameron, it has emerged that his wife, Samantha, and two of their children were with Mr Freud's party on his jet when it left Farnborough for the Mediterranean.

The aircraft then stopped off in Istanbul to pick up the Tory leader – who was returning from a visit to Georgia following the Russian military incursion – before flying on to Santorini.

Following drinks on the Rosehearty, Mr Cameron and his family attended a dinner party hosted by Mr Freud on his yacht, Elisabeth F.

Afterwards the Camerons were flown on the Gulfstream to Dalaman in Turkey where they joined Mrs Cameron's family for a sailing holiday to mark the 60th birthday of her mother, Viscountess Astor.

Meanwhile, according to The Independent newspaper, the Rosehearty sailed on to Corfu where Mr Murdoch held an on-board birthday party for his daughter, Elisabeth.

The guests were said to include Mr Osborne, Mr Deripaska and Peter Mandelson, then still the EU trade commissioner.

Mr Cameron's latest entry in the Register of Members' Interests declared: "16 August 2008, private plane from Farnborough to Istanbul for my wife and two children. Then from Istanbul to Santorini, and return to Dalaman, for myself, my wife and two children; provided by Matthew Freud, of London."

The Tories were dismissive of The Independent story. One source said: "This is a desperate attempt to make something out of nothing."

Meanwhile the Electoral Commission, which polices the party spending rules, has rejected calls for an investigation into Mr Osborne's conduct saying that it had seen no evidence of any offence.

Nevertheless the danger for the party is that the disclosures will create an impression of the party leadership as members of a gilded elite enjoying a life of luxury and privilege very different to ordinary voters.

It is in marked contrast to the rather more down-to-earth image Mr Cameron sought to present when he was photographed with his wife on a beach in Cornwall during the first leg of his holiday.

The Guardian, meanwhile, reported that Lord Mandelson's contacts with Mr Deripaska dated back earlier than has been previously acknowledged.

It is widely thought that it was Mr Osborne's disclosures about Lord Mandelson's meetings with Mr Deripaska while they were both guests of Mr Rothschild that prompted the financier to go public with his own claims about the shadow chancellor.

According to The Guardian, EU officials had said previously that Lord Mandelson, now the Business Secretary, had met the Russian "at a few social gatherings in 2006 and 2007".

However the paper said that the two men had been seen together by a journalist at a Moscow restaurant in October 2004 after Lord Mandelson was appointed trade commissioner but before he took up the post.

A Department for Business spokesman said: "Peter Mandelson's social and other contacts with Oleg Deripaska over a number of years have been well rehearsed.

"He does not believe anything is added by giving regular updates on dates and places where they met or in giving a retrospective running commentary of every meeting he has had with people he met during his time as EU trade commissioner.

"He is now focussed on his role as Business Secretary, helping businesses small and large to cope with the current economic downturn and to position themselves to come out stronger at the other side."