Sir Keir Starmer would lose his Commons majority if Robert Jenrick was the next Tory leader, a shock poll has revealed.

The former immigration minister would win an extra 57 seats, compared to the 30 Kemi Badenoch would claim, a study by Electoral Calculus said.

But the poll, of 6,300 people, also revealed one of the biggest beneficiaries of Tory members picking Mr Jenrick would be Nigel Farage and Reform UK.

It said the Conservatives, under Mr Jenrick, would win 178 seats.

Labour’s majority would vanish, with the party winning 311 seats, the Liberal Democrats dropping from 72 to 58 and Reform rising from five to 24. That would place Labour 14 seats short of a majority.

It is the first poll to examine the impact of the Conservative leadership candidates on a Parliamentary General Election.

Mr Jenrick seized on the polling, declaring to members: “This is the choice. Government or opposition.”

Surveys of Tory members suggest that Mrs Badenoch has the edge over Mr Jenrick, although the gap has narrowed. A YouGov poll of members at the beginning of Oc tober showed Mrs Badenoch ahead by 52 per cent to Mr Jenrick’s 48 per cent, compared with 59 per cent versus 41 per cent six weeks earlier.

A Jenrick campaign source said: “All the polling shows that Rob is more popular than Kemi with the public — whether they are Labour, Lib Dem or Reform voters.

“This is a contest to pick the next prospective prime minister, not just an opposition figure to shout at Starmer. Everyone has had enough of excuses and drama, we just need to deliver.”

Kemi Badenoch has said she is running a “grassroots campaign” to be the next Tory leader rather than a “media campaign”, in an apparent swipe at her rival Robert Jenrick.

The two final candidates for the Conservative leadership have taken different approaches to the final leg of the race to succeed Rishi Sunak, with Mr Jenrick having made more public-facing speeches than his rival.

Both are expected to take part in televised debates, including on GB News on Thursday.

But Ms Badenoch insisted that despite her lower profile early in the race, she was going win.

“I think we are going to do this. I am not being complacent,” she told a virtual rally of Tory members held on the platform Teams.

The North West Essex MP added: “I am working hard, I am running a grassroots campaign, not a TV campaign or a media campaign. I am getting out there and I am looking forward to meeting many of you on the campaign trail.”

In a wide-ranging question and answer session with Tory members, she claimed Reform UK and the Lib Dems were “two sides of the same coin” when asked how she would regain voters for the Conservatives.

She insisted the Lib Dems had gained so many seats in Parliament because Reform had split the Tories‘ vote, adding: “If we can get our vote back from Reform I think that would tackle quite a lot of the Lib Dem threat that we face. That means being confident Conservatives again.”

Ms Badenoch however said the party needed to “spread out and get the common ground back”, rather than “tack” in one particular political direction.