THE SNP is in an all-out push to woo Labour supporters as a new poll reveals that one in five people across the country will vote tactically in this week's General Election.

SNP leaders last night called on progressives to vote tactically for the party to loosen the Tories' grip on power. Nicola Sturgeon said Scottish voters now had the chance to ensure that "Tory austerity is consigned to the dustbin".

Her remarks came as she took to the air for a helicopter tour of 30 constituencies across Scotland between now and polling day on Thursday.

A new poll for the Electoral Reform Society has found that one in five people will be ‘holding their nose’ and voting tactically in the election against the party they most dislike.

When asked whether they’d be voting for a candidate or party best positioned to keep out someone they disliked, 20 per cent said they will. That compared to 58 per cent who said they will be voting for the candidate or party they most prefer.

The finding compares to a figure of just 9 per cent for a similar question asked in the run up to the 2015 election, and means that all is now to play for on Thursday when voters go to polling stations.

More than 2000 adults across the UK were interviewed for the poll by BMG Research. Darren Hughes, deputy chief executive of the Electoral Reform Society, said the findings showed the need to scrap the UK's first past the post electoral system and introduce proportional representation.

Hughes said: “It is frankly astonishing that a fifth of Brits feel unable to vote for their first choice party this election. That’s a huge proportion of people having to hold their nose and opt for a ‘lesser evil’ rather than who they actually support – and a significant and worrying rise on the last election. This is a situation foisted on voters by our arcane voting system – one that means people often feel forced to vote for their second or even third-choice party. "

Meanwhile, Angus Robertson, SNP deputy leader, warned that a vote for Labour in Scotland could allow the Tories to win seats by the backdoor and bolster Theresa May's majority.

Robertson said a Tory election win would unleash an "unprecedented assault" on working class and low income Scots.

He said: “In this election in Scotland, only a vote for the SNP can keep the Tories out. And a vote for Labour anywhere in Scotland just risks letting a Tory MP in by the backdoor. This whole election could turn on the result in Scotland, with the size of the Tory majority – or whether Theresa May gets one at all – down to the result here."

His remarks came as opinion polls showed the Tories are poised to make gains from the SNP. Robertson, one of the SNP's most influential figures, is facing an attempt by the Tories to oust him in Moray.

However, he warned that Tory gains in Scotland would make it easier for May to impose austerity on working families, pensioners and those on low incomes.

Robertson said: “There is a very real cost of voting Tory in this election - that is made abundantly clear in their manifesto. The Tories are planning nothing less than an unprecedented assault on the incomes of pensioners - abandoning the Triple Lock that guarantees fair state pension increases, cutting the winter fuel payment, and the notorious dementia tax.

“Any Tory MPs elected in Scotland will simply rubber-stamp whatever cuts the Tories are planning, and with the SNP placed first or second in every constituency in Scotland, a vote for any other party risks letting Tory MPs in by the back door.

“With polls narrowing across the UK, whether or not the Tories can increase their majority could come down to the votes in Scotland. I would urge all people in Scotland - even if they don’t normally vote SNP - to elect SNP MPs this Thursday to provide a progressive opposition to Tory cuts."

Meanwhile, Sturgeon began her helicopter tour in the final weekend of election campaigning by visiting six key constituencies yesterday in a branded helicopter - dubbed the "Nicolopter".

Sturgeon said the General Election offers voters a "golden opportunity" to dump austerity by voting against the Tories.

Sturgeon said: "There is a very clear choice on Thursday - you can either vote for a party which is committed to continuing its failed cuts agenda or you can vote for the SNP and demand that Tory austerity is consigned to the dustbin."

The SNP plea to Labour voters came as former Chancellor Alistair Darling said the idea of a so-called progressive alliance involving Labour and the SNP in the event of a hung parliament was "absolute nonsense".

Darling, who led the anti-independence Better Together campaign, was campaigning in Clarkston, East Renfrewshire, with Labour candidate Blair McDougall, former campaign director of Better Together, who is seeking to win back the seat Jim Murphy lost to the SNP in 2015.

Darling said: "If you look at things like health and education the nationalists' record in Scotland is atrocious. There's nothing progressive about educational standards going backwards, there's nothing progressive about longer waiting lists in the health service both of which the nationalists totally control, so I just think it's absolute nonsense."