Former Immigration Minister Robert Jenrick has said the Conservatives suffered a major defeat in the general election because the party failed to deliver on its promises to the public.
He added that the failure to cut migration was the crux of the election result.
He identified high taxes and broken public services as major causes for the defeat.
Mr Jenrick, who is on the right of the party and has been touted as a potential Tory leadership contender, did not rule out running to replace Rishi Sunak.
However, he said the first step was getting "the right diagnosis of what's gone wrong" and talk of leadership bids was "self-indulgent" at this stage.
Mr Jenrick, who resigned from Mr Sunak's government last year because he believed his Rwanda legislation did not go far enough, said: "The reason that we lost the trust of millions of people across the country is not because we were too left wing or right wing, or had this slogan or that slogan.
"But fundamentally because we failed to deliver on the promises we made to the British public."
The MP for Newark cited low economic growth, high taxes, the quality of NHS services and "above all" the failure to secure the country's borders and control migration, as examples of broken promises.
Mr Jenrick pointed to the loss of votes to Nigel Farage’s Reform UK party as evidence that migration "was at the heart" of the Tory defeat.
Reform, which had called for a freeze on non-essential immigration, won five seats and more than four million votes in the election.
The party also came second in 98 constituencies, in many cases pushing the Tories into third place.
Mr Jenrick said that in two-thirds of seats lost by the Tories, including those won by the Liberal Democrats, the margin of defeat was less than the Reform vote.