Pro-Brexit Tory MPs have agreed that staying in the EU customs union into the next decade is likely to be the “only viable option”, in a new report.

The cabinet’s failure to agree what kind of trading and customs arrangements it wants after the UK leaves the bloc is condemned by the Brexit Committee.

It concludes that, because neither option put forward by No 10 will be ready by the end of the planned transition in December 2020, remaining in the customs union for longer will be inevitable.

Significantly, the select committee’s members include Jacob Rees-Mogg and other leading Brexiteers – and its report is unanimous despite splits over key Brexit controversies in the past.

The committee also raises the alarm over the failure to explain how the rights of British citizens in other EU countries will be protected after Brexit.

While the Home Office had at least announced what EU citizens in this country will need to do, other member states “don’t appear to have begun to plan”, the MPs warn.

The criticisms come after HMRC appeared to torpedo the technology-based “max fac” proposal favoured by Brexiteers, after revealing it would cost businesses up to £20bn a year.

However, Theresa May’s preferred “customs partnership” – which would see the UK collect EU tariffs – has also been rejected by Brussels and cannot be implemented before 2023 anyway.

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

“We are rapidly running out of time to get new trade and customs arrangements in place,” said Hilary Benn, the committee’s Labour chairman.

“Given that ministers are indicating that neither of the two options being discussed are likely to be ready by December 2020, when the transition period ends, the UK will in all likelihood have to remain in a customs union with the EU until alternative arrangements can be put in place.”

The conclusion comes after Ms May told the EU she would accept a so-called backstop option to avoid a hard Irish border, keeping the UK partially aligned with customs rules after 2020.

The prime minister still argues it is unlikely to be needed, but the Brexit Committee disagrees and urges No 10 to set out “any contingency plans as a matter of urgency”.

Its report concludes: “The secretary of state [David Davis] has ruled out any extension of the customs union but, in the absence of any other plan, such an extension will be the only viable option.”

Mr Benn stressed that the clock is ticking to agree a solution for the Irish border, saying: “The EU is expecting clarification from ministers by the time of the European Council meeting in June about how the backstop will work.

“The government needs to come forward with its proposals as soon as possible to demonstrate how an open border, with no checks and no infrastructure, can be maintained.”

The Home Office has been criticised for failing to guarantee the full rights of the 3 million EU citizens in this country and for making them pay for “settled status” after Brexit.

But Mr Benn said the situation was more alarming for British ex-pats, warning: “EU member states don’t appear to have begun to plan for or communicate how British citizens will be able to regularise their stay.