The Tories hold a 15-point lead over Labour with less than four weeks to go to the general election on 8 June, according to the latest Opinium/Observer poll.

Despite the substantial gap, Labour under Jeremy Corbyn now has a larger share of the vote than that enjoyed by Ed Miliband in 2015.

The Conservatives are on 47% (up 1 point on a week ago), with Labour on 32% (up 2 points).

At the 2015 election, Labour took 30.4% of the vote. The Liberal Democrats are in third place on 8% (down 1 point) while Ukip is also down 1 point at 5%.

The survey suggests voters are increasingly opting for one of the two main parties as both of their vote shares increase.

Labour can take some comfort from having cut the Tory lead from 19 points three weeks ago, though the current 15-point difference would still deliver a thumping Commons majority of about 100 for Theresa May if replicated on polling day.

The share of the vote scored by Labour on polling day could turn out to be crucial in determining whether Corbyn stays on as leader in the event of a defeat for Labour.

Many Labour MPs believe he may try to hang on if he beats Miliband’s vote share, as he will be able to claim that the party is making progress and widening its appeal under his stewardship.

May remains ahead of Corbyn in the personal ratings. About 47% approve of the way she is running the country whereas just 23% approve of the way Corbyn is running Labour.

Ahead of the publication of party manifestos this week, there is substantial support for the idea of increasing taxation to pay for improvements to the NHS.

About 49% of people say they would be prepared to pay more if they knew it was going directly to the health service.

Just 21% said they disagreed with the proposal to pay more for the NHS through taxation.