LABOUR is now 11 points clear of the Conservatives, according to the latest poll from YouGov.
The survey, which was carried out on Wednesday and Thursday, has the Tories on 29 per cent, down four, while Labour are up one point to 40.
The LibDems are on 15%, their highest rating of this parliament.
Details of the poll came as backbench Tory MP Tom Tugendhat launched his campaign to replace Boris Johnson.
The chair of the Commons Foreign Affairs Committee - who has never served in government - said it was “time for renewal”.
Writing in the Daily Telegraph, he said he was “putting together a broad coalition of colleagues that will bring new energy and ideas to government and, finally, to bridge the Brexit divide that has dominated our recent history.”
“I have served before – in the military, and now in parliament. Now I hope to answer the call once again as prime minister. It’s time for a clean start. It’s time for renewal,” Mr Tugenhadt added.
He has the backing of at least five colleagues, including former ministers Damian Green and Stephen Hammond.
Mr Tugenhadt is, so far, the only Tory MP to have launched a formal bid for the top job.
Suella Braverman, the Attorney General, has expressed an interest.
She put herself forward on Wednesday night before Boris Johnson had resigned, saying it would be "the greatest honour" to serve.
Influential Brexiteer Steve Baker and chair of the Northern Research Group Jake Berry, have both also said that they could consider a bid for the top job.
The big-hitters have yet to declare.
Foreign Secretary Liz Truss, former health secretary Sajid Javid, Transport Secretary Grant Shapps, as well as ex-Chancellor Rishi Sunak, Defence Secretary Ben Wallace and ex-foreign secretary Jeremy Hunt are all possible contenders.
Penny Mordaunt, the International Trade Minister, is popular with Scottish Tories. She received the backing of John Lamont. He described her as an "effective communicator" on Times Radio and "strong on the Union".
He said the “ability to communicate a Conservative message across all parts of the United Kingdom” would be key for the next prime minister.
“There’s a number of strong candidates but the person who continually has impressed me during my time as an MP and prior to that as an MSP is Penny Mordaunt and I believe she is a very effective communicator, very strong on the Union,” said Mr Lamont, who ran Jeremy Hunt's disastrous leadership campaign in 2019.
David Mundell, the former Scottish secretary, said: “What we need, I think, is somebody who could unify the party, unify the country, frankly just be a little bit duller than the current incumbent and just really focus on getting the job done.”
Michael Gove and Dominic Raab have both ruled out a run at the leadership.
The 1922 Committee of Tory backbenchers will elect a new executive of 18 MPs on Monday, who will then decide the timetable for the leadership election.
It is likely that the first stage of the process, in which MPs vote the slate of candidates down to two, should be completed by July 21 when the Commons goes on recess.
Ballot papers would then be sent to the 100,000 party members across the UK to choose between the two remaining candidates, ideally in time for the return of parliament on September 5.