Nicola Sturgeon, Scotland's first minister, has accused the Scottish secretary of "dirty tricks" over the leak of the confidential memo which suggested she wanted David Cameron to remain as Britain's prime minister.
She was responding to the admission by Alistair Carmichael that the memo of her conversation with the French Ambassador had been leaked from his office, saying he should "question his whole approach to politics".
Mr Carmichael, a Liberal Democrat, had denied that the leak was an embarrassment to the Government, saying: "This is the middle of an election campaign, these things happen".
In response, Mrs Sturgeon said: "I think Alistair Carmichael really needs to question his whole approach to politics if he thinks dirty tricks and smear campaigns are just how things are done in elections.
"I take a very different view. I think elections should be a battle of positive ideas and that's how I'll continue to campaign."
Mr Carmichael has asked Jeremy Heywood, the cabinet secretary, to carry out an inquiry into the leak of the memo.
The SNP vehemently deny that Mrs Surgeon said she would prefer Mr Cameron to remain as prime minister, but the party has been less outspoken over the suggestion in the memo that she told Ambassador Sylvie Bermann she did not see Ed Miliband, the Labour leader, as "prime minister material."
Mrs Sturgeon said questions remained over how 'The Telegraph' came to have access to the memo. She said: "The questions are: who wrote this memo, how did it come to contain such an inaccuracy, but most importantly of all, how did it very conveniently fall into the hands of the 'Daily Telegraph'? I want answers to these questions and I want them as quickly as possible."
Scotland's first minister was speaking during a campaign visit in East Dunbartonshire, where she chatted with pensioners at a care home as she set out the SNP's plans to protect benefits for the elderly and raise pensions.
She said she was aware that she had become a more high profile figure since last week, when she was widely seen as having performed the best of the leaders taking part in a pre-election debate.
"We're challenging the old boys' network and we're challenging that cosy consensus of Labour, the Liberals and the Tories who want more austerity cuts," Mrs Sturgeon added.
"So, I guess it's not surprising there are people in the Westminster establishment who don't like that message and who want to fight back against it, but I'll continue to take our positive message to the doorsteps, the streets, the communities of Scotland, because I believe it's the right one."
Meanwhile a Conservative candidate will now represent the UK Independence Party at the general election amid disputed claims over whether he was sacked or defected.
Mike Whitehead was until this week the Tory candidate in Hull West and Hessle, a safe Labour seat which was held by former home secretary Alan Johnson. Nigel Farage, the Ukip leader, hailed his defection as a "hammer blow" to Conservative ambitions to be the main challenger to Labour in the north of England. But the Conservatives insisted that Mr Whitehead had been sacked a week ago after he refused to support a Tory candidate. (© Daily Telegraph, London)