The research showed a two-point rise for the Labour over the past week, which means the party has narrowed the Tories' lead in the polls by more than 13 points since the start of the campaign, the Guardian reported.
Campaigning in the city of Bath in England's West Country, May was asked about the YouGov poll which dominated the front page of the Times newspaper in London.
That is because markets initially pencilled in an increased Conservative majority - strengthening the Prime Minister's hand politically as she prepares for Brexit negotiations.
"While Labour's tax and spending plans are unlikely to win any friends in the financial sector, the party's more sanguine stance towards striking a trade deal during the Brexit negotiations might find common ground with some City grandees", she wrote.
YouGov's analysis puts the Tories on 310 seats, down from the 330 they went into the election campaign with, and 16 short of a majority.
The findings again weakened sterling GBP=D4 which had earlier fallen nearly a cent against the USA dollar on the YouGov model before rising on a Kantar poll which showed May's lead had increased to 10 percentage points.
A YouGov opinion poll on Wednesday showed the Conservatives' lead for the June 8 election had fallen to a fresh low of 3 percent. Labour is on 39 percent, up three points and its highest level since 2014, before Jeremy Corbyn became party leader.
In contrast to YouGov's model, other projections suggested May would win soundly.
When asked by a reporter if she would resign if she lost seats, May dodged the question on Wednesday, saying that the only poll that mattered was the election on June 8.
The poll indicated the Tories could lose 20 of the 330 seats they hold, and Jeremy Corbyn's Labour gain almost 30 MPs. May could actually lose seats on her party's 2015 General Election results, dealing a massive blow to her and her ability to negotiate on a Brexit deal in the immediate aftermath of the election.
"We shouldn't write off the thought that young people will turn out for this election (in large numbers) - but I think it's unlikely", Boon said.
Last night, Theresa May and Jeremy Corbyn took part in a televised interview with Jeremy Paxman, who quizzed the PM particularly about the U-turn on social care.
Labour would get 257 seats, up from 229, the Liberal Democrats 10, up from the nine Tim Farron's party held when the election was called, the SNP 50, the Greens one and Plaid Cymru three.
YouGov's chief executive, Stephan Shakespeare told The Times that the model used on this latest poll had been tested before the European Union referendum a year ago when it consistently put the Leave campaign in the lead.
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Here are highlights of the poll, as explained by Mollyann Brodie , senior vice president of Public Opinion Research at Kaiser. The CBO report did find that over time premiums would come down under the House bill, even if more people become uninsured.