Nicola Sturgeon, the SNP leader, has privately said that she would "rather see" David Cameron win the general election because Ed Miliband is not “prime minister material”, a leaked memorandum seen by The Telegraph has revealed.
The SNP leader told the French Ambassador in February that she would prefer that "David Cameron remain” in Downing Street, according to an official account of their conversation seen by this newspaper.
The disclosure undermines public claims made by Miss Sturgeon this week that she wants to build a "progressive" alliance with Ed Miliband and other left-wing parties to keep the Conservatives out of office.
It appears to confirm growing speculation in Scotland that the SNP would privately favour another Conservative-led Westminster government - which it could campaign against in a bid to stoke up anti-English sentiment and make an "out" vote more likely in another referendum.
The Telegraph has seen the official British Government memorandum which includes details of a private meeting between Miss Sturgeon and Sylvie Bermann, the French Ambassador to the UK.
The memorandum which was written by a senior British civil servant, dated March 6th, states: "Just had a telephone conversation with Pierre-Alain Coffinier (PAC), the French CG [consul-general]. He was keen to fill me in on some of the conversations his Ambassador had during her visit to Scotland last week. All of this was given on a confidential basis."
It continues: "The Ambassador....had a truncated meeting with the FM [Nicola Sturgeon, the First Minister] (FM running late after a busy Thursday…). Discussion appears to have focused mainly on the political situation, with the FM stating that she wouldn’t want a formal coalition with Labour; that the SNP would almost certainly have a large number of seats... that she’d rather see David Cameron remain as PM (and didn’t see Ed Miliband as PM material)."
The civil servant appeared so surprised by the private admission made by Miss Sturgeon that he questioned whether there might have been an issue with the "translation" during the conversation.
However, it was later established that the conversation took place in English as all the French officials are fluent.
It is a common diplomatic courtesy if an ambassador to the UK visits one of the three devolved administrations in Scotland, Wales or Northern Ireland for the British Government to be given an official readout of the conversation although the SNP leader, who has only been in position since the autumn, may have been unaware of this formality.
The disclosure of her private comments may undermine Miss Sturgeon's new-found popularity, after she was judged by snap opinion polls to have "won" Thursday night's general election debate with six other party leaders.
She is increasingly seen as a potential "kingmaker" in any Coalition talks as Labour support in Scotland has slumped with the SNP expected to gain dozens of seats in next month's general election.
Yesterday, Miss Sturgeon was mobbed after she returned to Scotland in scenes reminiscent of the "Cleggmania" recorded after the Liberal Democrat leader's success in the 2010 general election debates.
In other developments in the election campaign on Friday:
Mr Miliband was being urged by senior Labour MPs to consider pulling out of a second debate with Miss Sturgeon and other minority parties amid concerns that they will "hang the issue of austerity around his neck".
It was disclosed that Nigel Farage’s suggestion during the debate that foreigners with HIV should not be treated on the NHS was a carefully planned move to fire up Ukip’s core vote, a strategy insiders have dubbed “shock and awful”.
George Osborne, the Chancellor, and Michael Gove, the Chief Whip, repeatedly refused to rule out a power sharing agreement with Ukip in the event of a hung parliament.
A senior City figure warned of the damage that an uncertain election campaign may have on the financial markets
Despite official statistics saying that living standards are improving, Labour will release a campaign poster this weekend claiming that Tory policies cost families £1,100 a year
Miss Sturgeon’s comments may threaten the SNP’s huge opinion poll lead in Scotland, which is built on the support of traditional Labour voters who have grown disillusioned with the party but remain hostile to the Tories.
Yesterday, unaware that the memo had been leaked to the Telegraph, she continued to openly back Mr Miliband.
"If the SNP and Labour combined have more MPs than the Tories do - if there is an anti-Tory majority - we can lock David Cameron out of Downing Street," she said.
"I've challenged Ed Miliband, and I do so again: if we have that anti-Tory majority, the SNP has said we will vote to stop a Tory government even getting off the ground."
Jim Murphy, the Scottish Labour leader, and Willie Rennie, the Scottish Liberal Democrat leader, said the “astonishing” account of her comments proves that the SNP really wants a Tory Government with few or no MPs in Scotland, allowing the party to push the case for a second independence referendum.
Mr Murphy said: "This is a devastating revelation that exposes the uncomfortable truth behind the SNP's General Election campaign. For months Nicola Sturgeon has been telling Scots she wants rid of David Cameron yet behind closed doors with foreign governments she admits she wants a Tory Government. It's déjà vu all over again - the SNP say one thing in public but another private."
Mr Rennie said: “It is astonishing that Nicola Sturgeon can look people in the eye and declare the SNP would never support the Conservatives in government when in private she secretly wants them to win.
"Despite her fluffy, positive words about working with the rest of the UK this reveals her sole ambition is to break up the UK. I've no doubt that the Tories in government alone would fuel the Nationalist fires. She is open with foreign diplomats about her wishes now she needs to end the chicanery and be open with the voters."
Ms Sturgeon’s stated views in the document come after a number of opinion polls showed that Mr Cameron has significantly higher approval ratings in Scotland than Mr Miliband.
This week marked the beginning of Britain's general election campaign. The May 7 vote will decide whether David Cameron stays in Downing Street or whether his Labour rival, Ed Miliband, moves into Number 10 in his stead.