KEZIA Dugdale has said she has fallen victim to a dirty tricks campaign after details of a request for work experience with the SNP were leaked to a newspaper.

The Scottish Labour leader said she had "zero recollection" of writing to an SNP MSP asking for a work placement 13 years ago.

She did not deny the story - which appeared in the SNP-supporting Scottish Sun - but said : "I think this is the beginning of a dirty tricks campaign."

Scottish Liberal Democrat leader Willie Rennie called for the leak to be investigated by the Information Commissioner's Office as a potential breach of data protection laws.

The move follows anger among LibDems at the treatment of Alistair Carmichael, the former Secretary of State for Scotland, who was hounded by SNP after admitting leaking a memo designed to discredit Nicola Sturgeon during last year's Westminster election.

According to the Scottish Sun, Ms Dugdale wrote to SNP MSP Richard Lochhead in February 2003 asking for work as an unpaid researcher.

The story surfaced a few days after she said plunged her party's campaign into confusion by saying it was "not inconceivable" she would vote for independence as a means of keeping Scotland in the EU.

She later issued a clarification saying she opposed independence.

Speaking at a lunch organised by Holyrood journalists, Ms Dugdale said: "I think this is the start of a dirty tricks campaign.

"Why is this happening? Because I'm the only person in this election prepared to take on the big issue of of how we stop the cuts and end austerity in Scotland.

"The SNP are not prepared to match that commitment so they have decided to come after me instead.

"I supposedly applied for work experience, not a job, 13 years ago in February 2003 and I have absolutely zero recollection of this.

"I was a law student at the time, I was studying for my finals, I find the whole thing anathema.

"I don't know where it's come from."

She said the Sun, which supported the SNP in Scotland and the Conservatives in England at the last General Election, had not given her details of the story, adding: "So I'm not in a position to verify it."

She added: "I've the strong sense this is the start of a dirty tricks campaign."

The Sun quoted a "senior SNP source" who linked Ms Dugdale's application to her comments about independence.

The source told the paper she seemed was "very eager indeed to join the SNP" and that her recent remarks suggested she was "still keen on our policies".

In his letter to the Assistant Information Commissioner for Scotland and Northern Ireland, Mr Rennie said the leak could amount to a serious breach of data protection.

He wrote: "Scots deserve to know that employers collect, use and keep personal information appropriately and I would invite you to investigate this matter as I am deeply concerned about the implications for civil liberties in this country."

Ian Murray, the Scottish Labour MP and shadow Scottish Secretary, said: "The story itself was laughable but data protection is no laughing matter.

"People need to know that their correspondence with an MSP will be kept private, not leaked to a national newspaper for petty party politics."

He called on Nicola Sturgeon to condemn the leak.

Ms Sturgeon, campaigning in Leith, suggested the story was widely known and added: "I think it's probably more light-hearted than anything else.

"Maybe it says her political judgement was better when she was 21 than it is today.

"I'm not sure any of us, generally speaking, should be judged too harshly on the decisions our 21-year-old selves make and I think young people, if they've got an interest in politics regardless of their party affiliation, should be encouraged the get involved and get experience."

Ms Sturgeon's press team declined to say whether Mr Lochhead was involved in leaking information.

An SNP spokesman said: "Why the Lib Dems are being so po-faced about a light-hearted story which has already been laughed off by Kezia Dugdale is anyone's guess.

"It's clear they've resorted to diversionary tactics since they can't win votes on their deeply flawed policies.

"The fact Ms Dugdale asked for a position in the SNP has been very common knowledge in Holyrood circles for a long time.

"No documents of any kind have ever been given to any outside organisation."

A spokesman for the Information Commissioner's Office said: “We’re aware of this story.

"The law requires organisations to keep personal information secure, and to not keep it longer than is necessary.

"We’ll act where we see clear evidence that this hasn’t happened."