Kezia Dugdale has insisted reports she “supposedly” applied to work for the SNP more than a decade ago are “laughable”.
The Scottish Labour leader spoke out after it was reported she contacted the SNP looking for a position in both February and June 2003.
First Minister and SNP leader Nicola Sturgeon said: “I don’t think any of us should be judged too harshly on the decisions our 21-year-old selves made.”
She said the report suggested Ms Dugdale’s “political judgement was better when she was 21 than it is today”.
Ms Dugdale, 34, played down the story as she campaigned in Edinburgh in the run-up to May’s Holyrood election.
The Labour leader, whose father is a member of the SNP, told the BBC: “Thirteen years ago I supposedly applied for work experience in the Scottish Parliament.
“Now, I applied for lots of work experience, lots of young people at university do just that.
“The idea that this is a central issue of the Scottish election campaign is really laughable.”
Ms Dugdale is not understood to have been a member of the Labour Party at the time and she stressed she has never supported or voted for the SNP.
Ms Sturgeon, who was also campaigning in the capital, said the story was “probably more light-hearted than anything else” and added: “I think young people, if they have got an interest in politics, regardless of their party affiliation, should be encouraged to get involved and get experience.”