Alex Salmond had hoped to win a steady supply of concessions. Picture: Jane Barlow
In an interview with The Scotsman, shadow foreign secretary William Hague poured cold water on the prospect of a deal between the Tories and the SNP under which the Conservatives would grant a list of Nationalist demands in return for the SNP's parliamentary backing.
Alex Salmond has claimed Westminster could be "hung by a Scottish rope" if no one party wins an overall majority. He hopes that, along with Plaid Cymru in Wales, the two nationalist parties could hold the balance of power, enabling them to issue a series of demands to whoever is in power.
Current polls suggest that, while the Conservatives are set to be the biggest party, they may fall short of a majority, meaning they will have to seek support from other parties to win the confidence of the House of Commons.
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But asked yesterday whether he could envisage a so-called "confidence-and-supply" deal between the SNP and the Conservatives, Mr Hague replied: "Any observer would think that is a pretty unlikely prospect."
It is the first time the Tories have spoken out against a deal with the SNP.
Labour sources have also told The Scotsman they could not envisage a government-saving deal with the SNP in the event of a hung parliament.
Such a deal, which is short of a full coalition, involves the smaller party agreeing to back its bigger partner in key votes, in return for a steady supply of policy concessions.
In a wide-ranging interview, Mr Hague – who led the Tories between 1997 and 2001 – admitted their showing in Scotland over the past 13 years had been "deeply troubling". They have failed to return more than one MP at any election in that time. He added that if the Conservatives won the election but failed to win any more seats in Scotland, it would be "an incomplete victory".
He was speaking ahead of a visit by Conservative leader David Cameron to Aberdeen today, as the Scottish party aims to cut the 20-point gap between support for the Tories in Scotland and their support in the UK as a whole.
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Mr Hague, one of Mr Cameron's closest allies, would be involved in any post-election negotiations if there is a hung parliament. Mr Salmond said earlier this month that, in such a scenario, he hoped the votes of the SNP and Plaid MPs could be used as bargaining chips. He has ruled out any formal coalition with either the Conservatives or Labour, saying that he would instead seek to deal with a minority government as individual votes came along.
Similar case-by-case deals have been struck in the past, with parties such as the Ulster Unionists offering their support to the government on votes of confidence, in return for key concessions.
Mr Salmond has said that, for starters, he would demand complete control of all the money raised and spent in Scotland, including North Sea oil and gas revenues. But Mr Hague's comments appear to suggest any such deal with a minority Conservative administration is off the table.
Nonetheless, SNP Westminster leader Angus Robertson insisted his party would still be willing to work with either a Tory or Labour government. He said: "We have no intention of entering into coalition deals with either of the London parties. In a balanced parliament, the SNP will work on an issue-by-issue basis with whoever forms the government to secure a better deal for Scotland."
One constitutional expert said that, while the parliamentary arithmetic currently made an SNP-Tory deal extremely unlikely, there were precedents that supported the Nationalists' case.
Professor Robert Hazell, from University College London's constitution unit, said: "In 1978, Jim Callaghan was forced to turn to the Ulster Unionists for support after the Lib-Lab pact broke up. John Major also had to rely on the Ulster Unionists in 1996 after he lost his majority. So it is possible."
In Mr Callaghan's case, Labour agreed to give in to a key Ulster Unionist demand for greater representation in Northern Ireland.
But Labour's David Cairns said: "The SNP have spent years cosying up to the Tories and now William Hague has rebuffed them with one twirl of his helicopter's blades. This is utterly humiliating and underlines the SNP's status as a fringe party at Westminster."