Martin Baxter, who conducted the poll, said the research showed the Prime Minister must regain control of the centre-Right in British politics or risk losing the next election.

“The Conservatives at the moment are nowhere near an 80-seat majority,” he said.

“The issue right now is, are they going to win or lose? Boris Johnson was really successful last time in squeezing down the other Right-wing parties and unifying the Right-of-centre vote.

“That was the Conservatives’ secret weapon last time. If they lose that weapon, that is bad for them.”

A poll shows the Conservatives have lost nine points since May, and are just one point ahead of Labour, on 36 points compared to Sir Keir Starmer’s 35.

‘Channel deaths, fuel costs and sleaze’ contribute to drop in Tory support

Tory sources cited the fatalities during migrant crossings in the Channel, an increase in the cost of fuel and energy and a row over sleaze in Westminster as reasons for a drop in support for their party.

Concerns have also been raised about the quality of the Tories’ campaign in North Shropshire, while MPs heaped praise on Mr Tomlinson, who ran the operation for Mr French in Old Bexley and Sidcup.

“Bexley was the first by-election with [Mr Tomlinson] in charge – he set the pace, dictated strategy.”

But with memories of less well-run campaigns looming large, backbenchers are concerned his “bloody good result” can’t be replicated.

“The problem is there are too many [by-elections] at the same time – he can’t be everywhere,” one former minister said.

A senior party source said that to win the seat, the Conservatives must counter a strong Liberal Democrat presence by emphasising the Government’s action on illegal migration and Covid.

“They have got to get more positive communication of what the Government is doing,” the source said.

“Some of the ministers are doing fantastically, but others are not pulling their weight.”