THERESA May returned home yesterday from dinner with Irish Taoiseach Leo Varadkar to backstop warnings from her own party.

It was reported that conversation between the premiers ranged from “the latest Brexit developments” to the “ongoing political impasse in Northern Ireland”.

Varadkar previously said it was “not a day for negotiations” but an opportunity to “share perspectives”.

But the Prime Minister was dealt a warning from her own party after senior Tory figures wrote in the Telegraph newspaper that the “monumental” problems with her Brexit plan cannot be solved by “cursory tweaks”.

READ MORE: Tories warn May Brexit plan cannot be solved with 'cursory tweaks'

The message from the former Cabinet ministers furthers growing doubts over May’s ability to get a deal through parliament.

Brexiteers Iain Duncan Smith and Owen Paterson and Remainer Nicky Morgan penned the joint message, and were part of the group to help draw up the “Malthouse compromise”, which would see the backstop become a “free trade agreement-lite”, with no hard border but technical fixes and a longer implementation period.

“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 wrote in the Daily Telegraph.

May met Varadkar at Farmleigh House, where they were joined by the UK’s Brexit negotiator Olly Robbins and her chief of staff Gavin Barwell.

Varadkar said: “I believe ultimately we are going to have to get this deal over the line.”

Attorney General Geoffrey Cox also held talks in Dublin with his Irish counterpart, Seamus Woulfe.

Cox has been leading work within Whitehall on providing either a time limit on the backstop or giving the UK an exit mechanism from it.

Dublin rejects both, insisting the backstop cannot be time-limited if it is to provide an effective “insurance policy” against the return of a hard border.