Theresa May has been given a pre-by-election boost as the latest national opinion shows the Conservatives have climbed to a 18 point lead over Labour, ICM said on Monday (20 February).

The survey, of more than 2,000 people between 17 and 19 February, put the Tories on 44% (+2) and Labour on 26% (-1) – the highest lead for the Conservatives since 1983, when Michael Foot's Labour lost tens of seats against Margaret Thatcher.

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The data, commissioned by The Guardian, also comes just days before the Stoke-on-Trent Central and Copeland by-elections on Thursday 23 February.

Labour is defending the Staffordshire and Cumbrian constituencies following the resignation of Tristram Hunt and Jamie Reed from the House of Commons.

Hunt won a majority of more than 5,000 votes in Stoke at the general election, while Reed secured a majority of more than 2,500.

But Ukip leader Paul Nuttall is hoping to win over the 69% of Stoke residents who backed a Brexit at the EU referendum, and Conservative candidate Trudy Harrison is hoping to take advantage of Labour's weakness.

Losing two by-elections as an opposition party would be unprecedented. However, Jeremy Corbyn ally and Shadow Home Secretary Diane Abbott has said the Labour leader would stay on.

"We are hopeful of winning both of them, but it's really important that every Labour supporter comes out to vote," she told Sky News' Sophy Ridge show on Sunday. "And if we lost one or we lose both, the party will go forward, it has to go forward."

But Mike Gapes, the veteran Labour MP for Ilford South, stressed that a double by-election loss would be bad news for Labour. "A party heading for power would increase majorities in Stoke Central and ­Copeland, instead of fighting a rear-guard battle to save them," he said.

The ICM poll also found that Ukip were on 13% (+1), the Liberal Democrats were on 8% (-2) and the Greens were on 4% (unchanged).

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