This article is more than 1 year old

This article is more than 1 year old

The chief whip, Julian Smith, has warned cabinet ministers that, if MPs reject Theresa May’s deal a second time next week, parliament would take control and force a softer Brexit.

As part of attempts to win over Brexit-supporting ministers, Smith struck a pessimistic note on Tuesday about the parliamentary arithmetic, the Guardian understands.

He suggested the most likely outcome if the deal were rejected again would be that MPs opt to take a no-deal Brexit off the table and extend article 50. A softer Brexit would then emerge as the majority view in parliament, through a process of “indicative votes”.

The prime minister will announce a package of measures designed to safeguard workers’ rights on Wednesday as part of a last-ditch attempt to boost support for her deal and she is likely to fly to Brussels for talks before next week’s vote.

The workers’ rights pledges are aimed at winning over Labour MPs in Brexit-backing areas and followed the announcement on Monday of a £1.6bn fund for left-behind towns.

As well as promising votes on improvements to workers’ rights initiated by the EU, including two directives already in train, the government is pledging to consult trade unions and businesses on future workers’ rights proposals and create a single enforcement body for vulnerable workers.

However, trade unions dismissed the promises, with the TUC calling them “flimsy”.

Rebecca Long Bailey, the shadow business secretary, said: “Hot on the heels of their pathetic bribe for left-behind towns, here comes the government’s attempt to bribe workers to back their botched Brexit deal.

“Instead of automatically keeping up with European workers’ rights, and using that as a floor as Labour has pledged, the government is admitting that British workers could see their rights fall behind those of colleagues in Europe. This is utterly unacceptable.”

While it woos Labour MPs, Downing Street is also racing to secure clarifications over the status of the Irish backstop to placate the Brexit-backing European Research Group (ERG), which has established a “star chamber” of lawyers to examine any changes the attorney general, Geoffrey Cox, can secure in last-ditch talks over the next few days.

Even if the deal were approved next week, cabinet ministers believe a short, “technical” extension of a few weeks would be needed to pass the necessary legislation. But one senior Tory source said: “If we go for an extension of longer than a technical one, it will be long and it will lead to a softer Brexit.”

May has promised MPs an opportunity to reject a no-deal Brexit next week and is coming under growing pressure not to whip MPs in the crucial vote, which was secured after dozens of frontbenchers made clear they were prepared to resign.

Downing Street hopes the threat of a softer Brexit – including a customs union – will help to win over wavering Brexiters at the meaningful vote, which she has promised to hold by next Tuesday.

The long-delayed report stage of the trade bill – a key piece of Brexit legislation – is due to begin in the House of Lords on Wednesday, when a crossbench band of peers plan to reopen the issue of a customs union.

Lord Stevenson of Balmacara, the shadow international trade minister, said: “It is surely time for ministers to abandon their red lines and for the government to back this proposal.”

He added that if the amendment was passed, it would “give MPs an opportunity to think again about this crucial issue” when the legislation returned to the House of Commons, likely to be in late March, shortly before Britain is due to leave the EU.

That could give the House of Commons an opportunity to force the government’s hand if May’s deal has been rejected a second time by then. “It’s both a message – and a mechanism,” said one Labour source.

Supporters of the amendment include the former Tory pensions minister Lady Altmann and the crossbencher Lord Kerr.

Conservative MPs sounded negative on Tuesday about the prospect of May passing her deal, with one member of the government saying that No 10 appeared to be “in denial” about the parliamentary maths.

Another minister said it looked extremely unlikely that the deal would get through this time, unless the Democratic Unionist party buckled and took other Eurosceptics with them.

Cox visited Brussels on Tuesday to discuss the hoped for “legally-binding” changes to the Irish backstop demanded by Brexiters.

A spokeswoman for the prime minister said: “We are working at pace to secure the changes we need.” Asked whether the talks would be concluded in time for MPs to scrutinise any new legal text thoroughly, she added: “They will take as long as they need to take. They are obviously at a critical stage of the negotiations.”

The prime minister spoke to the Romanian president on Tuesday, and Downing Street said she would continue to consult with EU leaders throughout the week.