Opposing groups of Tory backbenchers launched rival bids to shape Theresa May’s Brexit plans on Wednesday, as the Prime Minister attempted to salvage a withdrawal deal with the European Union.

Prominent Conservative Eurosceptics led by Jacob Rees-Mogg ambushed Ms May in the Commons to push her into a harder position amid the fallout of the row over the Irish border.

Meanwhile, another group of Tories who previously backed Remain, including three ex-cabinet ministers, wrote to the Prime Minister urging her to put the interests of the UK economy first.

It comes as Ms May finally had a phone call with Democratic Unionist leader Arlene Foster on Wednesday, after her eleventh hour blocking of the Prime Minister’s attempt to gain a withdrawal deal.

Ms Foster had feared Ms May’s proposed Brexit settlement would see her compromise, by allowing Northern Ireland to remain in regulatory alignment with the EU. David Davis went further and said the whole UK could stay in regulatory alignment with the EU.

At Prime Minister’s Questions Tory Brexiteers who want the UK to break free from EU regulation, reminded Ms May of her stated intention to leave the customs union.

Among them was Mr Rees-Mogg, talked of as potential future leader, who said: “Before [Ms May] next goes to Brussels, will she apply a new coat of paint to her red lines?

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

“Because I fear on Monday they were beginning to look a little bit pink.”

The Prime Minister said the principles on which the Government is negotiating were set out in her Lancaster House and Florence speeches.

But Eurosceptic Bernard Jenkin MP stood up to hit home on the same issue, saying: “Would [she] confirm that she is aware of the very strong enthusiasm for free trade deals with the UK from countries like Canada, Japan, the United States, Australia and even for participations in the Trans-Pacific Partnership.

“But none of these opportunities will come our way if we remain shackled to EU regulation after we’ve left the EU.”

He was later joined by Peter Bone MP who reminded Ms May that the public had voted to leave the EU’s regulatory regime and offered to negotiate with the Prime Minister in Brussels if it would help.

From the other side 19 MPs wrote to the Prime Minister condemning their Brexiteer colleagues as “highly irresponsible” for urging her to walk away from the negotiating table.

Jacob Rees Mogg says May's Brexit 'red lines looking pink'

Among them were ex-cabinet ministers Nicky Morgan, Dominic Grieve and Stephen Crabb, who pushed the Prime Minister not to be swayed by Eurosceptic colleagues pushing for a harder Brexit.

They wrote: “In particular it is highly irresponsible to seek to dictate terms which could lead to the UK walking away from these negotiations.”

Ms May has pledged to protect the “constitutional integrity” of the UK in the negotiations to break the deadlock in the Brexit talks over the Irish border.

The Prime Minister said the Government was committed to ensuring there was no “hard border” between Northern Ireland and the Republic.