Theresa May’s claim to be building a “country that works for everyone” was dramatically undermined last night after the public body responsible for boosting social mobility resigned en masse in protest at her failure to tackle the issue.

The board of the Social Mobility Commission which includes two former cabinet ministers — one Tory and one Labour — resigned after concluding that the government’s focus on Brexit means that its ability to tackle social mobility “is zero”.

In a stunning rebuke for May, Alan Milburn, the commission’s chairman, accused ministers of abandoning the voters who had backed Brexit and of doing “nothing” to remove the grievances that had led to the referendum vote.

The commission’s annual report last week found that Britain has 65 “cold