ALEX Salmond has said he would welcome a pro-union pact aimed at thwarting his bid to return to Westminster and insisted that if an agreement was struck to field a single anti-nationalist candidate against him "the SNP will beat them as well".

There has been speculation that an informal alliance could be formed between the Liberal Democrats and Conservatives in an attempt to see the former First Minister off in the Aberdeenshire constituency of Gordon, where he will stand in next May's general election.

Despite retiring Liberal Democrat grandee Malcolm Bruce winning a majority of almost 7,000 in 2010, Mr Salmond said he believed that the Conservative candidate Colin Clark would be his main opposition.

However, senior Liberal Democrat sources insisted Mr Salmond was attempting to split the unionist vote in the seat, pointing out that the Conservatives finished in fourth place in 2010.

Mr Salmond said: "If the Liberal Democrats and the Conservatives put up a single candidate, then I hope they do because the SNP will beat them as well.

"The problem for the Liberals in the North East is that they have generated votes on the basis of being the anti-Tory Party. That's why Malcolm Bruce held Gordon. But you can't be anti-Tory and then go in to a coalition with them.

"Now that the Liberals are co-habiting with the Conservatives their whole reason for being has been taken away. That's why I believe the main opposition will come from the Conservatives."

Both the Liberal Democrats and the Conservatives have insisted they will fight to win the Gordon seat. Labour are not expected to mount a serious challenge with its local activists offering to help their former allies in the Better Together campaign, according to campaign insiders.

Aberdeenshire, Mr Salmond's political back yard, voted against independence by a margin of 60 per cent to 40 per cent in September and Liberal Democrat leader Willie Rennie has called on Labour and Conservative voters to rally behind his party's candidate, Christine Jardine, in May if they "don't want the distraction of independence to dominate again".

Michael Kelly, for former Labour Lord Provost in Glasgow, has urged Labour voters to back the Liberal Democrats and said Mr Salmond is "totally beatable in Gordon" and called for "just need one candidate against him".

Mr Salmond pointed to his success in Holyrood constituency of Aberdeenshire East, where he increased his majority from 4,500 to more than 15,000 at the 2011 Scottish Parliamentary election.

He said he would fight the election primarily as a constituency representative, but that the "overlying political issue" was how much power Scotland would wield at Westminster.

"During the referendum campaign people were promised devo-max, home rule and near-federalism," he added.

"These commitments were so blithely offered, now the chickens are coming home to roost. Come next May, there will be a few more chickens."

Mr Clark, a farmer and businessman, accused the Liberal Democrats of falling into a trap set by Mr Salmond and called Mr Rennie's suggestion that voters get behind a single pro-unionist candidate "naive".

"This has to be about the issues, not grievance," he said. "Alex Salmond wants to turn this into a rerun of the referendum, that is exactly what he is trying to ferment and people in Gordon do not want that. If there is one pro-union candidate, that's what it will turn into."

Ms Jardine said she believed voters would judge Mr Salmond on what he had done for the constituency in his seven years as First Minister.

"It speaks volumes that the former First Minister only wants to talk about himself, the voters in Gordon know I'm more interested in what really matters to them," she said.

"The voters will choose who they believe will be the strongest voice on the issues that affect them, not a backbench MP to continue to beat the drum for an independence cause they rejected."