But EU President Donald Tusk and European Commission President Jean-Claude Juncker also ruled out agreeing to anything “that changes or is inconsistent with” the deal.

The agreement between Britain and the EU was struck in November but has faced blockage in parliament as both pro-Brexit and pro-EU MPs have voiced opposition.

The issue of the backstop, a legal guarantee to keep the Irish border open whatever the outcome of negotiations on post-Brexit ties, has proved particularly contentious.

In the letter, the EU leaders said “the European Union does not wish to see the backstop enter into force” and only intended the backstop — if needed — to apply “temporarily”.

Juncker and Tusk said the deal represented “a fair compromise and aims to ensure an orderly withdrawal of the United Kingdom from the European Union, thereby limiting the negative consequences of Brexit”.

They said they were sending their letter “in order to facilitate the next steps of the process” and said their reassurances carried legal value. DM