Chris Huhne has sanctioned an extraordinary attack on Downing Street "dirty tricks", as his cabinet career hangs by a thread over his alleged attempt to cover up a speeding offence.
As the Crown Prosecution Service considers whether to bring charges against the Energy and Climate Change Secretary, friends of Mr Huhne accused David Cameron's press secretary, Gabby Bertin, of briefing against him over plans for a new royal yacht – a claim she denies.
The row is the latest twist in the saga surrounding the Lib Dem minister, who is also understood to be defying suggestions that he would be forced to resign from the Cabinet if he is charged with a criminal offence.
An ally of Mr Huhne pointed out that, under the ministerial code, if a minister is a defendant in a criminal case he or she does not automatically have to step down – it says only that government law officers should be consulted.
The defiance of Mr Huhne, one of only five Lib Dem ministers in the Cabinet, followed a row last week over the leaking of details of a replacement for the royal yacht Britannia. After The Guardian ran a story last Monday revealing that Michael Gove, the Education Secretary, was pushing for the yacht, Mr Huhne was blamed for being behind the leak.
The next day, the Conservative-supporting Telegraph pointed the finger of blame at the Climate Change Secretary, with the headline: "Huhne accused of leaking letter about new royal yacht."
The Telegraph followed up the story on Wednesday with a comment piece by Cristina Odone, who wrote: "Chris Huhne's attempt to smear the Tories had backfired." She added: "He has the cold, dead eyes of a political snake, hissing poison as he slithers down the corridors of power."
Yet Mr Huhne fiercely denied that he was behind the leak and obtained an apology from The Telegraph, which was published yesterday, for the news story and for the Odone article.
Friends of Mr Huhne last night claimed it was "common speculation" that Ms Bertin was the source of the allegation against him, and that a journalist rang her up to tell her she "shouldn't speculate about sources" and that in any event her alleged supposition was wrong.
A friend said: "What you cannot have is press secretaries trashing other members of the Cabinet. She has overstepped the mark and undermined her own credibility. That's back to the days of Blair. It's just gone too far."
Last night Ms Bertin, one of the Prime Minister's closest and longest-serving aides, rejected the claims by Mr Huhne's allies, insisting: "I have never briefed against Chris Huhne."
Mr Huhne could face charges of perverting the course of justice over claims that he asked his now ex-wife, Vicky Pryce, to take speeding points on his behalf. The Director of Public Prosecutions, Keir Starmer QC, could make the decision within days whether or not to charge the minister and Ms Pryce.
On Friday, Mr Huhne's speeding case dramatically changed gear when The Sunday Times withdrew an appeal against an earlier Crown Court judgment ordering the disclosure of dozens of emails sent by Ms Pryce to that newspaper. Essex Police demanded to see the emails as part of their investigation into allegations that Ms Pryce took speeding points on her husband's behalf. Detectives are said to have recommended that both should be charged.
Last night, friends insisted that the accusation against No 10 was not an attempt to deflect attention from the possible charges. One said: "He's characteristically bullish and confident. Vicky barely uses emails. It's the least important bit of the evidence. Chris is pleased The Sunday Times has come up with the emails as well."
The row is tantamount to a challenge to the Prime Minister – who is fiercely loyal to Ms Bertin, his press secretary of seven years' standing – to sack Mr Huhne. Mr Cameron has been urged to sack Mr Huhne for stoking divisions between the Tory and Lib Dem wings of the coalition. Relations between the two coalition partners are already tense after the Deputy Prime Minister, Nick Clegg, was unhappy with Mr Cameron's veto at the EU summit in Brussels last month.
The Climate Change Secretary, who was narrowly defeated for the Lib Dem leadership by Mr Clegg, clashed with the Chancellor, George Osborne, over the cabinet table at the height of Tory-Lib Dem warfare over the Alternative Vote campaign. Mr Huhne accused Mr Osborne of being behind personal attacks against Mr Clegg during the AV campaign.
Mr Huhne was unavailable for comment last night.