Leaks and more leaks. But who has the hidden agenda?

Andrew Neil, publisher of The Scotsman, was in a particularly ebullient mood at the Irish embassy Christmas party on Tuesday night. Amid the mince pies and Guinness, he is said to have told the throng ­ many delayed by Cherie Blair's televised mea culpa ­ that there were still more revelations to come on the affair.

We now know what they were. Yesterday's claim by The Scotsman that, contrary to her previous statements, Mrs Blair had received papers at No 10 relating to the immigration case involving the convicted fraudster Peter Foster, propelled the affair back to the top of the news agenda and embarrassed the Downing Street media machine yet again.

The statement by Carole Caplin, Mr Foster's girlfriend and Mrs Blair's style adviser, that the Prime Minister's wife had declined to look at the papers merely stirred an already heady brew.

The Scotsman story raised questions about Mrs Blair's professional position as a barrister and suggested she had not told the full story about her involvement with Mr Foster. It also led to speculation about who might have leaked the details ­ and why. It was the third time in a week that a selective leak had given the controversy renewed momentum.

The original disclosures, in The Mail on Sunday, about the links between Mr Foster and Mrs Blair received minimal coverage elsewhere. Not until the Daily Mail published e-mails confirming the relationship, which prompted Mrs Blair's apology for misleading the No 10 press office, did the story take off. According to the Mail, the e-mails came via business colleagues of Mr Foster in Australia. He had forwarded the messages after they doubted his claims of friendship with Mrs Blair. Mr Foster's friends deny that he orchestrated the leak and was paid by the Mail. "He is not in negotiation with them and has not received a penny from the Mail," one said, "but I do wish he would stop sending out e-mails."

According to transcripts of telephone conversations reported in The Sun today, Mr Foster says: "I may as well get something out of this."

On Monday, the story might have begun to fade after few disclosures in the Sunday papers, aside from reports that the Blairs had used money from their blind trust for the purchase of the Bristol flats in which Mr Foster had been involved. Then his solicitor, David Janes, released a statement confirming Mrs Blair had taken part in a telephone conference call with them to discuss his dispute with the immigration authorities. That led to Mrs Blair's emotional confession on Tuesday evening using a script said to have been devised by Labour's director of communications, Alastair Campbell. Cabinet ministers lined up to support her, and her husband issued an "I'm proud of my Cherie" statement. Classic Campbell tactics designed to draw a line under the affair, observers thought.

Then came the Scotsman story, which even included the precise time of the faxes, attributed to "legal sources".

The man at the centre of all this ­ a charming conman of legendary ability who has been jailed in three continents ­ remained closeted, as he has done for most of the past 10 days, in Ms Caplin's flat in one of the less fashionable parts of Islington, north London. Ms Caplin had been pregnant by him, but miscarried last week.

There is no doubt that the situation has been aggravated by boasts Mr Foster made about his relationship with the Blairs to business associates he was recruiting to sell his latest slimming aid.

His appeal seems to have delayed his deportation for at least two months. The Home Office has failed to explain why his entry to the UK was not challenged until August, although he had been in and out of Britain earlier in the year. He met Ms Caplin in London in July.

However, evidence emerged last night that Mr Foster had targeted Ms Caplin because of her friendship with Mrs Blair. A former business associate, Mike Carroll, told Tonight with Trevor McDonald that Mr Foster said: "Not only is she [Caplin] connected, she's a bit of a babe."

According to Mr Carroll, a salesman, he was contacted by Mr Foster in June about a company called Renuelle which he was setting up in the UK to market a slimming product. Mr Carroll said he suggested to Mr Foster that the Government might be interested in the venture.

"It was like a little light switched on. He said: 'I've got a friend coming over this weekend ... whose best friend is very close to Cherie Blair.' He said: 'I'll have a look at that one'," Mr Carroll said. He said he reported Mr Foster to the Fraud Squad after he realised the slimming pill business was a scam.

It was revealed last night that Mr Foster sent a video message to Tony Blair three years ago admitting he was a "white collar criminal" ­ but no gangster. Mr Foster recorded the message in his Brisbane prison cell as part of his unsuccessful legal battle to fight extradition to Britain on fraud charges. On the tape, obtained in Australia by Channel 4 News, he appealed to the Prime Minister for help.