SNP surge would please David Cameron, says Labour frontbencher

David Cameron will be “secretly pleased” at the prospect of Labour losing dozens of seats to the Scottish National party, a senior member of the shadow cabinet has claimed.

Margaret Curran, the shadow Scottish secretary, said the prime minister “will have a smile on his face, hoping people vote SNP” at the general election as that would boost his chances of staying in Downing Street for a further five years.

“We know David Cameron is actually secretly pleased with the prospects of Scottish people voting SNP because he knows that’s his best chance of being in power,” she said.

Cameron is due in Edinburgh on Friday to address the Scottish Tories’ spring conference. A series of opinion polls have indicated the SNP could win several dozen seats from Labour, potentially denying Ed Miliband an overall majority at Westminster.

Labour is seeking to shift the emphasis on to the Tories and Cameron even though there is minimal direct threat from the Conservatives in any Scottish Labour seat. The party is scared of openly attacking up to 200,000 former supporters who are now expected to back the SNP after its performance in last year’s independence referendum campaign.

The Tories expect to be the only one of the three major pro-UK parties in Scotland to maintain their share of the vote in May, possibly winning one or two extra seats after more than a decade with just one Scottish MP. They believe that a collapse in support for the Lib Dems puts several rural seats within touching distance, and they expect to become Scotland’s third largest party by share of the vote.

The Tories’ quest to widen their appeal stepped up a gear when Ruth Davidson, the Scottish Tory leader and the party’s first openly gay leader, appeared in an election broadcast with her new partner, Jen Wilson. The party would not release any biographical information about Wilson, who had a brief appearance in the broadcast with Davidson’s parents, but confirmed the two were a couple.

The Tories are emphasising their unionist credentials by explicitly ruling out any post-election deal with the SNP – a prospect also rejected repeatedly by SNP leader, Nicola Sturgeon, and her predecessor Alex Salmond. Davidson stated in the broadcast: “Scotland just voted to stay part of the UK, so let’s build on that.”

Cameron is expected to attack Labour and the Lib Dems for leaving open the prospects of a post-election deal with the SNP and the Green party in England in his speech on Friday. Vince Cable, the business secretary, said the Lib Dems would consider a cross-party coalition deal involving Labour and the SNP after the election if there was a hung parliament. “It’s certainly possible,” he said on Tuesday. “I wouldn’t rule it out.”

After refusing to rule out a deal with the SNP three times last week, on Wednesday Labour’s Curran again refused to rule out a post-election coalition, claiming it would be “presumptuous” for politicians to prejudge an election. “We’re not in the business of pre-empting the election,” Curran said. “I absolutely believe that we can and will work and deliver a majority Labour government.”