The Conservative lead over Labour has been slashed to a single point, according to a new opinion poll which suggests the election race is neck and neck.
The Survation poll for Good Morning Britain (GMB) put the Tories on 41.5 per cent with Labour on 40.4 per cent.
If such a result were replicated on Thursday it would put the Conservatives' majority in Parliament in jeopardy.
But opinion polls by other leading polling firms have given wider leads for the Conservatives in recent days, ranging as high as 11 and 12 points.
The Conservatives had a 17-point lead with the pollster at the start of May, but Labour's rise reflected a campaign which more than half of those polled thought had been better than Theresa May's.
The latest poll was conducted on Friday and Saturday, before an attack in London by Islamist militants killed seven people and injured 48.
In the previous Survation poll for ITV, published a week ago, the Conservatives had a lead of six points.
But a separate Survation poll, published on Saturday for the Mail on Sunday, also gave the Conservatives a one-point lead.
The latest poll put the Liberal Democrats on 6 per cent and Ukip on 3 per cent.
It was based on interviews with 1,103 people and the data was weighted to be representative of all UK adults.
Three weeks ago, a series of surveys showed Ms May was on course for a landslide parliamentary majority which she called to secure a strong mandate for Brexit talks.
But her campaign began to struggle after she proposed a plan to make elderly people pay for more of their social care, a so-called "dementia tax," even though she moved quickly to say there would be a limit on the amount of costs that people would face.
It remains unclear whether Saturday's terror attack will have an impact on the election.
The Conservatives' lead over Labour continued to fall after a suicide bombing in Manchester on 22 May, but polling firms have linked the narrowing to the rival parties' policy proposals rather than the attack.
Fifty per cent of respondents in the poll thought Ms May would make a better prime minister than Jeremy Corbyn, but his credibility as a potential leader of the country has risen to 36 per cent from 15 per cent in early May.
Several other polls are due to published before voters go to the polls on Thursday.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies