Jeremy Corbyn is on course to win Labour's biggest share of the vote in a general election for more than a decade, according to a YouGov poll released on Monday (1 June).

The survey of more than 1,800 people between 30–31 May put the Conservatives on 42% (-1) and Labour on 39% (+3). The figures, if replicated on 8 June, would see Corbyn beat Tony Blair's share of the vote in 2005, when more than 35% of the electorate backed Labour.

The result would also see the Tories lose 15 seats to Labour, with Theresa May facing a hung parliament, forcing her to form a coalition government with smaller, rival parties.

The research comes just a week before the general election and during a campaign which has seen the Conservative poll lead plummet from as high as 24 points.

May faced a backlash over her so-called "dementia tax" plan. The policy would see elderly voters in England have to pay for their social care costs if they own assets worth more than £100,000.

But despite the unpopularity of the proposal, May is more than 10 points ahead of Corbyn (43 versus 30) in personality ratings. Labour's vote share performance could be crucial to Corbyn's political future, with the left-winger refusing to say if he would quit if he loses the general election.

Corbyn supporter, author and journalist Owen Jones told IBTimes UK that he should leave the top job if he fails to increase Labour's vote share or gain seats on 8 June.

"If he doesn't make any progress in the election, then of course [he should go]," Jones said in May.

He added: "The leadership has to show that it has a vision that can inspire people, not just people that have joined the Labour Party full of enthusiasm, but the people out there who have better things to do than talk about politics."

May's political future would also be in doubt if she fails to secure a majority. The prime minister called the general election in a bid to strengthen her hand at the Brexit negotiating table, but the move could backfire.