THE SNP has rebuffed an advance from convicted perjurer Tommy Sheridan to become more deeply involved in the independence campaign.

After Sheridan appeared on TV to promote the cause, Finance Secretary John Swinney denounced him as "a man of no political credibility whatsoever" at a fringe meeting at the SNP conference.

Swinney's remarks came after the Solidarity leader and former Glasgow MSP appeared on the BBC political show This Week on Thursday night as an advocate for independence.

In a studio discussion on Friday with former Tory minister Michael Portillo and former Labour spin doctor Alastair Campbell, Sheridan, who took part in last month's march for independence, played up his role in the fight. He referred to "We in the independence campaign" and said "What Alex [Salmond] and I would agree on...".

However, Swinney's reaction suggests the SNP leadership views Sheridan as potentially poisonous to the campaign.

Sheridan, 48, was jailed for three years in January 2011 for lying under oath in his 2006 defamation action against the News Of The World, which had claimed he was an adulterer and swinger.

He was released a year later.

Rather than welcoming him as a potential ally, Swinney implied the BBC had been mischief-making by putting him on TV.

He told a fringe meeting organised by the National Union of Journalists: "Is it just me, or is anyone else surprised that, miraculously, in the midst of the SNP conference, the BBC have managed to provide a platform for the rehabilitation of Tommy Sheridan as an independence advocate?

"A man who has no political credibility whatsoever – none whatsoever. Not even political credibility, no credibility in terms of the judgments made by the courts of the land. But, miraculously, last night... that appears. What's that about?"