A YouGov poll for The Times newspaper has found that for the first time since June's Brexit vote more British voters believed that the decision to leave the European Union was a mistake than those who thought it was the right decision.
45% of respondents thought it was the wrong decision compared to 43% who said it was correct; 12% said they did not know.
British voters split 52-48% in favour of leaving the EU at the referendum, which the British government has said cannot be reversed.
Theresa May, who replaced David Cameron as prime minister shortly after last June's referendum shock result, repeatedly ruled out a snap election, before announcing on 18 April that she planned an election on 8 June.
She is seeking to bolster her majority in parliament ahead of potentially disruptive EU divorce talks and has gambled that the low level of support for the Labour Party under left-wing leader Jeremy Corbyn gives her a good chance to achieve that.
The YouGov poll also suggests her party holds a 16-point lead over the main opposition Labour Party, a smaller lead than other polls have suggested.
It put support for the Conservatives at 45%, down three percentage points from a YouGov poll conducted last week.
Labour increased its support by four points to 29%, while the Liberal Democrats were down two points at 10% and UKIP rose two points to 7%, The Times said.
The poll findings excluded "don't knows" and "would not vote" responses.
The YouGov poll suggested a somewhat tighter race than the picture painted by two surveys published yesterday which had shown the Conservatives enjoying leads of 23 and 22 points over Labour.
One of those two polls, by Ipsos MORI, said the lead of the Conservatives was equal to that commanded by former prime minister Margaret Thatcher before her 1983 landslide victory.
