The European Parliament’s Brexit chief has poured cold water on Theresa May’s plan to solve the Northern Ireland border issue, just hours after the PM released revised proposals designed to placate both Brussels and Brexiteers in her own Cabinet.

Reaction from the European Commission to the UK’s white paper has been polite but cautious, with chief negotiator Michel Barnier saying they would examine the proposals to see whether they were up to scratch. Mr Barnier said the plan would have to respect the integrity of the single market, and be a “workable solution” to the border of an “all-weather” character.

But Guy Verhofstadt, who has taken the role as a vocal outrider for Brussels during Brexit negotiations, said on Thursday afternoon that the plan did not look workable.

He warned that it was “difficult to see how [the] UK proposal on customs aspects of the Ireland/Northern Ireland backstop will deliver a workable solution to avoid a hard border and respect integrity of the single market and customs union”, adding that “a backstop that is temporary is not a backstop, unless the definitive arrangement is the same as the backstop”.

European Commission officials said they were studying the proposals while British diplomats in Brussels said they would begin to talks over the plans. Also commenting shortly after the release of the latest plan, Mr Barnier said: “I welcome publication of UK proposal on customs aspects of Ireland/Northern Ireland backstop.”

“We will examine it with three questions: is it a workable solution to avoid a hard border? Does it respect the integrity of the single market and customs union? Is it an all-weather backstop?”

The Prime Minister emerged from a Cabinet row today after Brexiteers demanded that the so-called “backstop” plan for the Irish border be strictly time-limited. Brexit Secretary David Davis had reportedly threatened to resign over the issue: he and other Brexiteers fear that plans to align the whole UK with the single market and customs union until another way of preventing a hard border was found would amount to keeping Britain tied to EU rules indefinitely.

Mr Davis appears to have carried the day, as the proposals say that “the temporary customs arrangement, should it be needed, should be time limited, and that it will be only in place until the future customs arrangement can be introduced”. But the white paper is, again, light on detail, and says only that “there are a range of options for how a time limit could be delivered, which the UK will propose and discuss with the EU”. British diplomats did not provide any more information about what these options might entail.

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

EU officials have said that in order for substantial progress to be made on Brexit at an upcoming Brussels summit later this month, Britain would have to accept that the backstop could not be time-limited and that it would have to only apply to Northern Ireland, rather than the whole UK.