The Nationalists are also on course to seize former Liberal Democrat leader Charles Kennedy’s Highland seat and employment minister Jo Swinson’s East Dunbartonshire constituency, according to the survey of key Scottish seats.
It is now increasingly likely that Labour leader Ed Miliband will need SNP support to secure the keys to Downing Street, as he again refused to rule out a post-election pact with First Minster Nicola Sturgeon yesterday.
Mr Murphy is now nine points behind the SNP in his East Renfrewshire seat, having been one ahead two months ago, according to polling by Lord Ashcroft.
The SNP should also capture the Glasgow South West seat of Ian Davidson, the survey of eight key Scottish constituencies finds, as well as the Liberal Democrat stronghold in North East Fife which Sir Menzies Campbell is vacating.
Mr Miliband repeatedly refused to rule out a post-election coalition with the SNP on the campaign trail yesterday after his TV debate clash with Ms Sturgeon on Thursday. The SNP leader pleaded with Mr Miliband to do a deal which would lock David Cameron out of Downing Street.
The Prime Minister sought to ramp up fears about higher borrowing and taxes if Ms Sturgeon props up a Labour government.
In a Twitter post, the PM said: “Ed Miliband won’t rule out a vote-by-vote deal with the SNP so he can be PM. It would mean more borrowing and more taxes and you would pay.”
Mr Miliband said his message to the First Minister was “thanks, but no thanks” but declined to give a guarantee that he would not turn to the Nationalists for support on a vote-by-vote basis if the outcome of the General Election is inconclusive.
The Labour leader added anyone watching Thursday’s televised leaders’ debate would have seen “fundamental differences between Labour and the SNP on the economy, national security and the break-up of the UK”.
He said: “I think lots and lots of people are jumping way ahead here. I’m working for a majority Labour government. I believe we can win a majority Labour government. Let’s actually see what happens on 7 May.”
The First Minister said Mr Cameron’s only route back to power if the election produces “an anti-Tory majority” would be “if Ed Miliband stands back and lets him into Downing Street”. She added: “If Ed Miliband and Labour do that, they will not be forgiven.”
Meanwhile, a Survation poll handed the Tories a narrow lead across the UK. It placed them up four points on 34 per cent, ahead of Labour on 33 per cent, down two points. Nationally, the SNP had a 4 per cent share.
SCOTSMAN TABLET AND MOBILE APPS