A government bid to find a compromise to win over rebels before the Commons Brexit vote has run into criticism.
A Tory backbench amendment – understood to have No 10’s backing – offers MPs more of a say over the contentious issue of the Northern Ireland backstop.
DUP leader Arlene Foster dismissed it as “legislative tinkering” while Tory Brexiteers said it was “desperate”.
Many MPs have expressed concerns about the backstop, aimed at preventing a “hard border” on the island of Ireland.
It would mean Northern Ireland staying aligned to some EU rules, which many MPs say is unacceptable.
The UK would also not be able to leave the backstop without EU agreement.
Cabinet ministers are travelling around the UK on Friday as Theresa May continues to seek support for her Brexit deal.
The withdrawal deal negotiated between the UK and EU has been endorsed by EU leaders but must also be backed by Parliament if it is to come into force.
MPs will decide whether to accept it next Tuesday, but dozens of Tories are expected to reject it, as will the DUP, whose support keeps Mrs May’s government in power.
Downing Street has dismissed reports the vote could be delayed, although the chairman of Tory backbenchers, Sir Graham Brady has said he would “welcome the vote being deferred” if it meant concerns about the backstop could be addressed.
But Health Secretary Matt Hancock told BBC Radio 4’s Today programme that “the best thing for the country” was for MPs to back Mrs May’s deal: “I think we should win the vote, don’t pre-judge it.”
“My view is we should continue the debate. We’ve had three days, there’s two days more. I think we should make the argument, make the case and persuade people – that’s what you have Parliamentary debate for.”
The prime minister has suggested that MPs could be “given a role” in deciding whether to activate the backstop, and on Thursday night, a Tory backbench amendment was laid down intended to do that.
The amendment – which is understood to have government support – would also give the devolved administrations, particularly the Northern Ireland Assembly, although it is currently suspended, more say in the process.
It would also press the UK and EU to agree a future trade deal within a year of the implementation period ending.
Former Northern Ireland minister Hugo Swire tabled the amendment along with Bob Neill and Richard Graham.
Mr Swire told the BBC the amendment offered something that was “better than the current situation”.
Many Tory MPs would like to see the backstop “disappear altogether or be time limited”, he said, but the European Commission had said they would not re-open negotiations on the withdrawal agreement, so the amendment was “about the nearest we feel we can probe”.
He added that MPs could either accept that “the writing is pretty much on the wall as far as voting goes this week or people like me, who would like to be able to support this deal but find they are unable to, have to do what we believe is in the national interest which is try to get some kind of resolution to it.
“And the only way we can do that at this stage is by putting down these sort of amendments”
Maddy Thimont Jack, from the The Institute for Government think tank, said that any amendment would not be legally binding but was “a political expression of will from Parliament”.
But she added that the EU was unlikely to want to include a Parliamentary vote on the backstop within the withdrawal agreement, a legally binding international treaty.
So if Parliament voted against implementing the backstop, should the situation arise, there was a possibility that the UK “would end up violating the terms of the treaty and therefore the treaty itself would fall”.
Conservative Brexiteer Steve Baker dismissed the amendment: “Giving Parliament the choice between the devil and the deep blue sea is desperate and will persuade very few.”
And one senior source from the Conservative European Research Group told the BBC the amendment was “transparent and risible”.
DUP Leader Arlene Foster tweeted: “Domestic legislative tinkering won’t cut it. The legally binding international withdrawal treaty would remain fundamentally flawed, as evidenced by the attorney general’s legal advice.”
Ministers ‘speaking with communities’
Five days before MPs vote on the deal negotiated with the EU, Chancellor Philip Hammond, Health Secretary Mr Hancock, Cabinet Office Minister David Lidington Scottish Secretary David Mundell will be among those trying to sell it to the public in visits across the UK.
Theresa May said in her own visits across the UK “overwhelmingly, the message I’ve heard is that people want us to get on with it. And that’s why it’s important that ministers are out speaking with communities across the UK today about how the deal works for them.”
But in an article in the Guardian, Labour Leader Jeremy Corbyn said the deal represented a “monumental and damaging failure for our country” and represented “a worst of all worlds deal, that works for nobody, whether they voted leave or remain”.
He confirmed that, if the deal was rejected and Labour’s preferred outcome – a general election – was not on offer, “all options” remained on the table, including “the option of campaigning for a public vote to break the deadlock”.