Writing in the Telegraph, Leave campaigners Owen Paterson and Iain Duncan Smith, alongside Remainer Nicky Morgan, said the controversial insurance policy for maintaining an open border in Ireland must be replaced entirely – something the EU has ruled out.
Mrs May was forced to seek fresh concessions after MPs rejected her Brexit deal by a record-breaking 230 votes.
Criticising the Prime Minister’s approach to the negotiations, the three ex-ministers write that “it is almost as if the Prime Minister has forgotten the scale of the original Withdrawal Agreement’s defeat or how unacceptable the Backstop proposals remain to significant numbers of MPs on both sides of the House”.
They said that by adopting the so-called Malthouse Compromise, which seeks an extension to Article 50 and the removal of the backstop, “the Government will honour its commitment to the people of Northern Ireland that they will remain an indivisible part of the United Kingdom and, above all, deliver Brexit on time and in full”.
Their intervention comes as it emerged that further attempts to remove a no-deal Brexit as an option were being discussed by a cross-party group of MPs.
The Huffington Post reported that an amendment designed to give Parliament the ability to stop no deal is “highly likely” to be proposed when MPs debate Brexit again on Thursday.
A former Tory Minister and Labour MP said that there is “substantial consensus” on the issue.