SNP aide Mark MacLachlan forced to quit over smears

•Alex Salmond: his Damian McBride moment?

Mark MacLachlan, 46, has been forced to quit as Michael Russell's office manager after he used his blog and other electronic communications to spread abusive and defamatory messages about senior Labour and Tory figures.

The revelation, which echoes the resignation of prime ministerial aide Damian McBride earlier this year after an internet dirty-tricks campaign came to light at Westminster, is deeply embarrassing for Alex Salmond and Russell as it comes the day before they launch the SNP's Referendum White Paper, which they hope will lead to Scottish independence.

MacLachlan, whose 30,000 job in the minister's Dumfries constituency office was funded by the taxpayer, published a blog titled "The Universality of Cheese" under the pseudonym Montague Burton, which promoted the nationalist cause.

The blog contained false allegations about the sex lives and behaviour of politicians and other prominent people in public life.

Among those smeared were Lord Foulkes, the Labour MSP, Paul McBride QC, the lawyer and high-profile Tory, members of the shadow cabinet and Labour councillors.

The general secretary of the Scottish Labour Party, Colin Smyth, is intending to sue for damages after malicious comments were published about him.

The fact that the allegations have been made by a figure so close to such a key government minister is highly damaging for the SNP and will inevitably draw comparisons with the Damian McBride affair, which rocked Gordon Brown earlier this year. McBride, one of Brown's most trusted advisers, resigned after the Prime Minister said there was "no place" in politics for the "juvenile and inappropriate" e-mails that he had sent from a Downing Street address.

McBride's e-mails made unfounded claims about Tory leader David Cameron and shadow chancellor George Osborne and led to scathing criticisms about the conduct of the UK government.

"This is Alex Salmond's Damian McBride moment," said Tavish Scott, the Lib Dem leader. "We need an apology from him and for him to disassociate himself from this blogger immediately.

"This poisonous SNP bile attacking anyone who dares criticise Alex Salmond's nationalists was paid for by the Scottish taxpayer. I want a full investigation by the Permanent Secretary into what other SNP special advisers, researchers and hired hands are involved in this kind of odious politics."

Scott added: "If Mark MacLachlan posted any of his defamations and smears in office hours, while being paid by the taxpayer and while using facilities provided at the taxpayers' expense, Mike Russell's position is untenable and Alex Salmond should sack him."

Russell's spokesman has said that the minister knew "absolutely nothing" about MacLachlan's online activities.

Iain Gray, the Scottish Labour leader, also called on Salmond to apologise. "By his silence Alex Salmond condones it," he said. "In May, Labour called on him to root out the campaign by cybernats after disgusting attacks not just on politicians but also on journalists who don't toe the SNP line. As First Minister it is his duty to personally apologise for this filth."

Scottish Tory leader Annabel Goldie said: "This politics of vile hatred is abhorrent. Behind the smiles, the nasty underbelly of the SNP has been exposed. People are judged by the company they keep."

The Universality of Cheese blog was taken off the internet on Thursday night after it was discovered that it was being run by MacLachlan.

Yesterday, MacLachlan, who has also resigned from the SNP, said: "I deeply regret my actions and unreservedly apologise to all the people concerned, and to Mike Russell. In getting carried away with my comments, which were very wrong, I have let myself and my colleagues down, and of course I have resigned from my position in Dumfries."

Russell's spokesman added: "Mike was shocked to be told about this on Thursday evening, he knew absolutely nothing about it, and has accepted Mark MacLachlan's resignation."