Brexit: MPs to vote on 'right to terminate' Irish backstop after speaker selects amendments to tonight's vote on May's deal

But bid to impose a strict 'sunset clause' on the backstop - which could have prevented Theresa May's humiliation - will not go ahead

MPs are set to vote to demand the UK has the power to pull out of the Irish border backstop, ahead of the landmark clash on Theresa May’s Brexit deal.

An amendment to secure a unilateral “right to terminate” – potentially putting the UK on a fresh collision course with the EU – has been selected by the Commons speaker.

However, John Bercow did not select an even more controversial attempt to impose a strict “sunset clause” for the backstop, of the end of December 2021.

Although not formally backed by the government, the second amendment was favoured by many Tories who hoped it could win support and prevent the expected humiliation of a heavy defeat.

They also believed the prime minister would have been able to show the EU what concession was required to eventually pass her deal, in the weeks to come.

It was suggested Mr Bercow had rejected the “sunset clause” amendment because it had, in reality, been tabled by the government – but disguised under the name of a backbencher’, Andrew Murrison.

The Speaker’s decisions mean there are now likely to be five votes on total tonight, suggesting the clash on the so-called meaningful vote will take place around 8.30pm

However, the Democratic Unionist Party scotched rumours that it would support any last-gasp attempt to make the backstop – demanded by the EU, to prevent the return of a hard border – more palatable.

“Amendments tabled in parliament will have no bearing on the legal status of what has been negotiated. What is required is for the prime minister to go and secure legally-binding changes as she promised,” a spokesman said.

“Today's very belated amendments are part of the internal parliamentary games and do not change the need to secure legally-binding changes.”

The four amendments selected were tabled by Labour, the Scottish Nationalist Party and two Tory backbenchers - Edward Leigh and John Barron, which aims to secure the “right to terminate”.

Labour’s amendment rejects the prime minister’s deal and demands a customs union, a closer single market deal, plus protections on the environmental and workers' rights.

The SNP wants the government to “request an extension to the period of negotiation under Article 50 of the Treaty on European Union”.

Sir Edward’s amendment also concerns the Irish backstop, seeking for the UK to use prior international law to ensure there can be no “indefinite continuation of the backstop”.

Geoffrey Cox, the attorney general, said the government would not accept it because it would fall foul of the UK’s international law obligations and be viewed, by the EU, as not ratifying the divorce deal.