I have no absolutely no idea what his motive was but I think it will repulse delegates at the SNP conference

John Swinney

He attacked an unnamed senior figure for seeking to have the party foot the bill for a return air fare to Brussels for his wife, who was accompanying him.

Mr Blackford consistently refused to name the official but the allegation prompted a furious denial from outgoing convener Alex Salmond, who said the party had received a refund for the cost of the fare.

Mr Salmond said delegates at the conference would show their feelings about Mr Blackford when they voted in a new treasurer on Saturday afternoon.

On Friday, Mr Swinney and Mr Neil said they would not let the controversy overshadow the party's sixty sixth annual conference in Inverness.

Alex Salmond: Rejected allegations

Mr Swinney said: "I think it's a shame that the whole issue has reared its head at an important conference where there's many things happening, where there's buoyant opinion polls for support for the Scottish National Party, where the SNP's doing extremely well.

"That one of our members has decided to go down this particular route, I think it's absolutely contemptible," he told the BBC's Good Morning Scotland programme.

The present deputy leader said he did not want to speculate on what had motivated Mr Blackford, a Neil supporter, to speak out.

"I have no absolutely no idea what his motive was but I think it will repulse delegates at the SNP conference, who detest these kind of things going on," he said.

'No prior knowledge'

Mr Neil refused to condemn Mr Blackford but denied any prior knowledge of the exiled treasurer's plans to speak out at a critical time, a day before Mr Salmond's final address as party leader.

He said: "This is a leadership contest, there's no way I'm going to get embroiled in a row about who paid for whose air fair in 19-canteen.

"There are far, far bigger issues to discuss about the future of Scotland, about the future of independence.

Delegates at the conference

"And the whole saga, over the past few months, which I think has been badly handled, is one I think we need to learn lessons from.

He strongly denied suggestions that Mr Blackford launched his attack on Mr Neil's behalf.

Turning to the predominant campaigning issue - the timetable for independence - the candidates were again at loggerheads.

Mr Neil said the party leadership had been "too timid" in its approach to the Scottish Parliament and must use it as a platform to achieving independence.

Mr Swinney said he also wanted to see "independence tomorrow" but that mandate would be achieved when the party has won the Scottish parliamentary elections.