The Conservative lead in the polls has plunged just three days after the launch of its manifesto.
Theresa May's party has seen its lead halve in a week due to a lack of support for manifesto policies, concerns over NHS funding, and the unpopularity of changes to the funding of social care.
A poll by YouGov for the Sunday Times, which was conducted after the manifesto was released on Thursday, has seen the Tory lead slashed overnight, with the Conservatives down to 44% and Labour rising to 35%.
If voting at the 8 June general election mirrored this poll it would still deliver a decisive Tory victory, but with a smaller majority than the 150-seat landslide that some polls and commentators have predicted.
Only 35% of those who responded to the survey supported the Tory proposal to shake up how people pay for social care, while 40% said they opposed the policy.
May's nine-point lead in the polls is the smallest recorded for the prime minister so far this year.
A separate poll, published by Survation, has put the Conservatives on 46% and Labour on 34% – a 5% fall in support for the Tories – while other polls by Opinium and ORB had the Tory lead down to 13 and 12 points respectively.
The Tory manifesto has been criticised by Labour and by pensioner advocacy groups who fear older people will struggle to meet the cost of social care and winter fuel payments if the Tories' plans are carried out.
An unnamed Conservative minister quoted by the Sunday Times urged May to "quickly change the subject", telling the paper that the manifesto plans on care were not going down well with voters.
"We need to get off care and pensioner benefits and start talking about the calamity of Corbyn again," they said.
Separately, YouGov's poll for the Sunday Times on Sunday also suggested that the Tories' poll lead would remain unchanged even if a more centrist Labour figure was leader, such as Sadiq Khan, Chuka Umunna, or Yvette Cooper.