Tory MPs have warned the party could cease to exist if it breaks its pledge to cut immigration before the next election.
Members of the New Conservatives group said the party faced a “do or die” moment after new figures showed net migration had trebled since 2019.
According to the Office for National Statistics (ONS), 672,000 more people entered the UK than left it in the 12 months to June.
The Tories’ 2019 general election manifesto pledged to bring it down to less than 229,000.
In a statement published on X (formerly Twitter), the New Conservatives said the party could not afford to break that “solemn promise”.
“The word existential has been used a lot in recent days, but this really is ‘do or die’ for our party,” they said.
“Each of us made a promise to the electorate. We don’t believe that such promises can be ignored.”
The group, which is largely made up of MPs in the Red Wall seats the Tories won from Labour at the last election, called on the government to produce “a comprehensive package of measures to meet the manifesto promise by the time of the next election”.
They added: “The prime minister, chancellor and new home secretary must show that they stand by the promises on which we were elected to parliament. We must act now.”
Miriam Cates, on of the members of the group, said: “Today’s UK migration figures are astounding: a million new people from abroad were added to our population last year. There is simply no democratic consent for this.
“Attempts to reduce NHS waiting times or solve the housing crisis are futile unless we drastically reduce numbers.”
The Times reported that the PM is looking to announce new plans to curb migration over the next week because of fury on the Tory backbenches over the issue.
Sky News reported that home secretary James Cleverly had promised the government was still “completely committed to reducing levels of legal migration, while also focusing relentlessly” on illegal migration.
From July 2019 to June 2023, the total estimated UK net migration stood at over 1.6 million.
The Office for Budget Responsibility has also estimated that an extra 150,000 migrants would arrive in the next five years – adding around 1.5 million people to the population by 2028-29.