Jean-Marie Le Pen is at the centre of an SNP row

She said the SNP leader's letter to her was an "insurance policy" for Mr Swinney to ensure he was not labelled similarly.

Mr Swinney told BBC Scotland: "I told Margo MacDonald, both in writing and in a meeting my profound disagreement with her about the article she wrote.

"I want to make it equally clear that the SNP holds the policies of Jean-Marie Le Pen in total contempt."

He added: "His politics have no place in our democratic debate."

Mr Le Pen shocked French politics last Sunday when he won through to the second round of the presidential elections.

'Trying to understand'

French President Jacques Chirac, who faces Mr Le Pen in a run-off on 5 May, called for national unity to defeat "extremism".

Speaking on BBC Radio's Good Morning Scotland programme Ms MacDonald said she was not a fascist, a racist, nor did she give succour to Mr Le Pen.

"When I said that his logic was difficult to fault it was in direct relation towards young children who were legal or illegal immigrants into France and who he said were ghettoised," Ms MacDonald said.

President Chirac, 69, is seeking a second term

"Because he said he wanted them to be French and to share in the benefits of the best culture in the world ever known."

The MSP said she was "very interested" in why five million voters in France did vote for him.

"Everything I knew about the man from a distance was repugnant to me. So I was trying to understand why people were voting for him."

She said rather than giving the stock response to Mr Le Pen's success at the polls and what he stood for, it was constructive to ask why he still had a foothold in French politics.

The MSP used to be a television journalist and interviewed Mr Le Pen about 10-years ago - that meeting formed the basis for a column she wrote in the Edinburgh Evening News.

'Party politics'

Ms MacDonald wrote: "When I tackled Le Pen about his attitude to the thousands of other people who had emigrated, legally or illegally, to France from all over the African continent, his logic was difficult to fault.

"He explained skin colour was of no consequence to him, neither was country of origin. What he objected to, he claimed, was that people, by clinging to the cultures of their home countries, ghettoised themselves and their children.

Le Pen has inspired angry protests in France

"He said he wanted everyone of these immigrant children to grow up as French citizens."

Ms MacDonald described the letter she had received from Mr Swinney as a "different thing altogether".

She said: "He told me in a meeting that he did not believe me to be racist or fascist, but the letter was an insurance policy in case anyone called him a racist or a fascist.

"And the fact that it was leaked is internal party politics which I have no intention of discussing."

BBC Scotland political correspondent Kirsten Campbell said there had been suggestions the SNP was attempting to discredit Ms MacDonald as the party goes through the process of selecting its candidates for next year's Scottish elections.