A letter from Theresa May has led DUP leaders to fear that she will renege on a promise to prevent any division between Northern Ireland and the rest of the UK Jack Taylor/Getty Images

Theresa May’s de facto deputy has warned that any Brexit deal with the EU will have to involve compromise as the DUP accused the prime minister of “breaching” her pledge not to allow Northern Ireland to be divided from the rest of the UK.

After meeting the Irish prime minister, Leo Varadkar, David Lidington did not address DUP concerns directly but warned any agreement would have to involve “give and take”.

He was speaking after a leaked letter from the prime minister to the DUP revealed the government is preparing to allow the EU to impose specific regulatory checks on goods entering Northern Ireland as part of the controversial backstop.

It also suggests that the final Withdrawal Agreement could contain a mechanism to put a…