Theresa May is poised to hand pro-hard Brexit MPs a victory by accepting a raft of changes to customs legislation in votes tonight.

The European Research Group – led by Jacob Rees-Mogg – has put down four amendments to the taxation bill, as it bids to force the prime minister back to a hard Brexit stance.

Her spokesman signalled a climbdown when he told reporters: “We will consider the amendments and set out our position in due course.”

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It appeared that the government might accept all four amendments – in the belief that doing so would not wreck the Chequers plan for tariffs, even before it reaches Brussels.

The most significant would prevent the UK collecting duties for the EU unless Brussels agreed reciprocal arrangements, which the Brexiteers believe would kill off the prospect.

But a government source suggested this would not conflict with the Chequers proposal, dubbed the facilitated customs arrangement (FCA).

By early on Monday, it had been signed by 11 Tory MPs including former leader Iain Duncan Smith, former cabinet minister Priti Patel and Mr Rees-Mogg.

Although, with Labour opposed, the government did not face defeat, the clash set up a show of strength which the ERG hopes to exploit and the prime minister is desperate to avoid.

If the number of rebels tops 48, it would exceed the tally required to force a vote of no confidence in Ms May’s leadership of the Conservative party.

Brexit threatens life on the Irish border: in pictures Show all 15 1 /15 Brexit threatens life on the Irish border: in pictures Brexit threatens life on the Irish border: in pictures An abandoned shop is seen in Mullan, Co Monaghan. The building was home to four families who left during the Troubles. The town was largely abandoned after the hard border was put in place during the conflict. Mullan has seen some regeneration in recent years, but faces an uncertain future with Brexit on the horizon Reuters Brexit threatens life on the Irish border: in pictures A defaced ‘Welcome to Northern Ireland’ sign stands on the border in Middletown, Co Armagh Reuters Brexit threatens life on the Irish border: in pictures Mervyn Johnson owns a garage in the border town of Pettigo, which straddles the counties of Donegal and Fermanagh. ‘I’ve been here since 1956, it was a bit of a problem for a few years. My premises has been blown up about six or seven times, we just kept building and starting again,’ Johnson said laughing. ‘We just got used to it [the hard border] really but now that it’s gone, we wouldn't like it back again’ Reuters Brexit threatens life on the Irish border: in pictures Farmer Gordon Crockett’s Coshquin farm straddles both Derry/Londonderry in the North and Donegal in the Republic. ‘At the minute there is no real problem, you can cross the border as free as you want. We could cross it six or eight times a day,’ said Crockett. ‘If there was any sort of obstruction it would slow down our work every day’ Reuters Brexit threatens life on the Irish border: in pictures John Murphy flies the European flag outside his home near the border village of Forkhill, Co Armagh Reuters Brexit threatens life on the Irish border: in pictures Potter Brenda McGinn stands outside her Mullan, Co Monaghan, studio – the former Jas Boylan shoe factory which was the main employer in the area until it shut down due to the Troubles. ‘When I came back, this would have been somewhere you would have driven through and have been quite sad. It was a decrepit looking village,’ said McGinn, whose Busy Bee Ceramics is one of a handful of enterprises restoring life to the community. ‘Now this is a revitalised, old hidden village’ Reuters Brexit threatens life on the Irish border: in pictures Union Flag colours painted on kerbstones and bus-stops along the border village of Newbuildings, Co Derry/Londonderry Reuters Brexit threatens life on the Irish border: in pictures Grass reflected in Lattone Lough, which is split by the border between Cavan and Fermanagh, seen from near Ballinacor, Northern Ireland Reuters Brexit threatens life on the Irish border: in pictures Donegalman David McClintock sits in the Border Cafe in the village of Muff, which straddles Donegal and Derry/Londonderry Reuters Brexit threatens life on the Irish border: in pictures An old Irish phone box stands alongside a bus stop in the border town of Glaslough, Co Monaghan Reuters Brexit threatens life on the Irish border: in pictures Billboards are viewed from inside a disused customs hut in Carrickcarnon, Co Down, on the border with Co Louth in the Republic Reuters Brexit threatens life on the Irish border: in pictures Seamus McQuaid takes packages that locals on the Irish side of the border have delivered to his business, McQuaid Auto-Parts, to save money on postal fees, near the Co Fermanagh village of Newtownbutler. ‘I live in the south but the business is in the North,’ said McQaid. "I wholesale into the Republic of Ireland so if there’s duty, I’ll have to set up a company 200 yards up the road to sell to my customers. I’ll have to bring the same product in through Dublin instead of Belfast’ Reuters Brexit threatens life on the Irish border: in pictures A disused Great Northern Railway line and station that was for customs and excise on the border town of Glenfarne, Co Leitrim Reuters Brexit threatens life on the Irish border: in pictures Alice Mullen, from Monaghan in the Republic of Ireland, does her shopping at a former customs post on the border in Middletown, Co Armagh. ‘I’d be very worried if it was a hard border, I remember when people were divided. I would be very afraid of the threat to the peace process, it was a dreadful time to live through. Even to go to mass on a Sunday, you’d have to go through checkpoints. It is terribly stressful,’ said Mullen. ‘All those barricades and boundaries were pulled down. I see it as a huge big exercise of trust and I do believe everyone breathed a sigh of relief’ Reuters Brexit threatens life on the Irish border: in pictures A bus stop and red post box stand in the border town of Jonesborough, Co Armagh Reuters

However, some of the prime minister’s Tory opponents believe any no-confidence vote must be called by Wednesday this week if it is to be staged before parliament breaks up for the summer on Tuesday next week.

The other three ERG amendments to the taxation (cross border trade) bill – formerly known as the customs bill – appear easier for the government to accept.

One would require the UK to have a separate VAT regime from the EU, while another would require the government to table primary legislation if it wishes to keep Britain in a customs union.

The last would enshrine in law that there cannot be a customs border down the Irish Sea – a border Ms May has repeatedly ruled out anyway.

Nevertheless, accepting the last amendment would be seen as provocative by Brussels which has floated the idea as a “backstop” measure, needed to secure a withdrawal agreement.

There are suggestions that the ERG could agree to pull the amendment requiring reciprocity on tariff collection if the government accepts the other three.

But Steve Baker, who quit last week as a Brexit minister in protest at the Chequers plan and who is “whipping” Tories for the ERG, insisted that was “wrong”.

Earlier, Greg Clark, the business secretary, urged pro-Brexit Tory colleagues to recognise that the bill was “essential” and must not be obstructed.