The Conservative Party will “die” unless it proposes pulling Britain out of the European Convention on Human Rights (ECHR), Robert Jenrick will claim on Monday.

In a speech at a rally at the Tory conference in Birmingham, Mr Jenrick, the front-runner in the party’s leadership race, will further harden his rhetoric on immigration.

He will warn that Nigel Farage’s Reform party will “grow and grow and condemn us to obscurity” unless the Tories somehow regain trust on bringing down numbers.

The warning is Mr Jenrick’s latest attempt to put the UK’s membership of the ECHR at the centre of the leadership contest.

Kemi Badenoch, James Cleverly and Tom Tugendhat, the other three candidates vying to replace Rishi Sunak, have declined to explicitly call to leave the convention.

Instead, they have argued that the UK immigration system needs to be overhauled first.

The ECHR, which defends universal human rights and was shaped in part by Winston Churchill, has been increasingly debated amid the Channel migrant crisis.

‘Restoring our credibility’

Mr Jenrick, who quit as Mr Sunak’s immigration minister last year, argues the convention is too limiting on the UK’s ability to deport those who arrive by such crossings.

In a speech today, Mr Jenrick will point to both his promise to cap annual net migration at 100,000 and to leave the ECHR, warning of the consequences of not pursuing the two policies.

Mr Jenrick will say: “Our party’s survival rests on restoring our credibility on immigration. If we continue to duck and dance around this question our party has no future.

“Despite what others might falsely claim, we’ve never had a legal cap on legal migration. Unless we introduce one – where no visas will be issued unless net migration is in the tens of thousands or lower – we will be powerless to end the cycle of broken promises. Anyone who is not prepared to commit to a specific cap just doesn’t understand the depth of public anger.

“I am not prepared to gamble the house on some five-year review process that may or may not see us doing what is obviously necessary. I have a plan ready now: leave the ECHR and introduce a legally binding cap on legal migration.

“The choice is clear, it’s leave or remain. In fact it’s more than that – it is leave or die. If we don’t do this now, we’ll never restore the public’s trust and there’s every chance that Reform will grow and grow and condemn us to obscurity.”

The “leave or remain” phrase appears to be a deliberate attempt to echo the rhetoric of the Brexit referendum. Most Tory members voted to leave the EU back in the 2016 vote, according to polling analysis.

‘Not out of conviction’

On Sunday, Mr Farage took a swipe at Mr Jenrick, saying: “Formerly a man that believed in nothing, Robert Jenrick now pitches himself as the great hardliner. This is almost certainly done for political gain and not out of conviction.”

Mr Jenrick topped the last round of Tory MP voting, with Ms Badenoch in second place. Tory MPs will whittle the list down to two next month before party members pick the winner.

Ms Badenoch, the former business secretary, countered Mr Jenrick’s position in an article for The Telegraph this weekend.

Ms Badenoch wrote: “We will end illegal migration by proper enforcement and inserting whatever deterrent is necessary into the system. And, yes: if necessary, we will leave international frameworks like the ECHR which were built for another age and are being bent out of shape by legal activism.

“But that will be part of a full plan, not just a throwaway promise to win a leadership contest. Reducing immigration is our objective. We lost sight of that in government.”

Ms Badenoch, appearing on BBC One’s Sunday with Laura Kuenssberg, was also made to defend another aspect of her article.

She was questioned on her remark that “numbers matter, culture matters even more” when it comes to immigration.

Pressed on this, Ms Badenoch said: “We are not a dormitory. This is our home. People from all around the world just living here in their little bubbles and little groups is a recipe for disaster.

“I have seen it… I grew up in a country with 300 ethnic groups. This is a recipe for conflict, and the government needs to work hard on integration.”

But Mr Jenrick, who has committed to capping net migration in the tens of thousands or below, said he disagreed with her approach because “numbers also matter”.