Nicola Sturgeon has said reports that she told a French ambassador she would prefer to see a Conservative victory at the General Election are "categorically, 100%, untrue".
The Daily Telegraph claimed a UK Government memorandum written after Scotland's First Minister met Sylvie Bermann in February detailed her preference for David Cameron remaining in Downing Street.
The note, seen by the newspaper, was written by a British civil servant after a conversation with the French consul-general.
According to the Telegraph, it said: "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."
Campaigning earlier today, Ms Sturgeon said a strong showing for her party in the election could help ''lock the Tories out of government''.
The SNP leader responded on Twitter to one of the Telegraph journalists who wrote the story, saying: "your story is categorically, 100%, untrue ... which I'd have told you if you'd asked me at any point today."
A spokeswoman for the First Minister added: "As the First Minister has said, this story - which is based on a UK Government document - is categorically, 100% untrue. It must be a belated April Fool.
"As Nicola has said on numerous occasions, she wants to see the back of a Tory government which is decisively rejected by the people of Scotland and unlike Labour, the SNP is the only party that has promised to lock David Cameron out of Downing Street."
As she returned to the campaign trail after the leaders' debate yesterday, t he First Minster said the SNP and Labour would constitute an ''anti-Tory majority'' if the two parties together secure more MPs than the Conservatives on May 7.
She was welcomed by cheering activists in Edinburgh after her appearance in ITV's televised debate where she shared a platform with six other leaders.
Polling after last night's programme showed Ms Sturgeon had been well-received both north and south of the border, with Defence Secretary Michael Fallon admitting today ''she certainly outshone the other challengers''.
Responding to the Telegraph story, Scottish Labour leader Jim 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.
"We've been here before with the SNP. It's deja vu all over again - the SNP say one thing in public but another private.
"If Scotland votes SNP in May then Nicola Sturgeon will get her wish - the Tories will be the largest party across the UK and David Cameron will return to Downing Street. Only a vote for Labour will deliver a Labour government."