Theresa May has been accused of “shafting” Northern Ireland over Brexit by pandering to the DUP and her hardline Eurosceptic MPs.

The Prime Minister faced criticism on a visit to Belfast as business leaders and nationalist politicians warned her not to ditch the so-called ‘backstop’ plan designed to keep open the province’s border with Ireland.

Apparently stung by the criticism, May insisted that she would not in fact dump the ‘insurance policy’ and even suggested that she may not go ahead with a hi-tech trade monitoring scheme proposed by Brexiteer Tory MPs.

That in turn sparked an angry response from the backbench European Research Group (ERG), which has called for the backstop to be ripped out of the May’s deal with the EU.

Last week, MPs voted for an amendment tabled by Tory grandee Sir Graham Brady which “requires the Northern Ireland backstop to be replaced with alternative arrangements to avoid a hard border”.

The PM used a speech to business leaders to stress that she would never do anything to undermine the Good Friday Agreement, the accord which ended years of bloodshed as Unionist and nationalist parties agreed a peace deal.

But local reporters pointed out that her recent decision to cave to pressure from Brexiteers and the DUP risked throwing away the advantages of the ‘backstop’ plan, to keep trade flowing with the EU and UK.

Suzanne Breen of the Belfast Telegraph asked: “Prime Minister, given that many business figures in this room may feel that you betrayed and shafted them on the backstop in your recent U-turn, why should they believe any of the pledges you made to them today?”

May replied: “Let’s be very clear about this. You’ve used the phrase U-turn in your question.

“There is no suggestion that we are not going to ensure that in the future there is provision for this – it’s been called an insurance policy, the backstop – that ensures that if the future relationship is not in place by the end of the implementation period, there will be arrangements in place to ensure that we deliver no hard border.”

Ulster TV’s Ken Reid asked May if she owed an apology to the people of Northern Ireland – who voted by 56% to Remain in the EU in the 2016 referendum.

May replied: “I’m not proposing to persuade people to accept a deal that doesn’t contain that insurance policy for the future.

“What parliament said is that they believe there should be changes to the backstop.”

In her speech, the PM had also given a clear signal that she may not go ahead with ‘technological’ solutions that Brexiteers have suggested could solve the problem, with trusted trader and other number-plate recognition cameras away from the border.

May said that the open border in the Good Friday Agreement was “the cornerstone around which the community in Northern Ireland has come together to deliver peace and prosperity”.

“And I will not do anything to put that at risk. So while I have said that technology could play a part, and that we will look at alternative arrangements, these must be ones that can be made to work for the particular circumstances of Northern Ireland,” she said.

The reaction was swift from the Brexiteers’ ERG group, with one source saying: “Even if she doesn’t mean what she said, we still do.″

One senior Tory MP told HuffPost UK hard Brexit colleagues could only back the deal if the backstop is removed entirely and replaced with the “alternative arrangements” set out in the so-called ‘Malthouse compromise’ plans drafted by Tory MPs.

There would also have to be no checks between Northern Ireland and the Irish Sea and Britain must be able to leave the alternative arrangement of its own accord, the MP said.

However a separate Brexiteer source said Tories could accept the backstop if there was a clear unilateral exit mechanism, which appears a more likely compromise with the EU.

It could take the form of a two-year exit mechanism, similar to Article 50 for leaving the EU, they said.

This would have to be backed up by written legal advice from the Attorney General Geoffrey Cox stating that the UK would not be trapped in the backstop.

A statement to the House of Commons would not be enough, they added, pointing out that Lord Goldsmith’s comments on the legal case for the Iraq War to the Lords were far more political and less explicit than his written advice for the government, the source added.

May will miss Prime Minister’s Question Time on Wednesday as she holds talks with Ulster’s various political parties. On Thursday, she will visit Brussels for fresh talks, but a spokesman for EU Commission President Jean-Claude Juncker said the EU was still “waiting once again to hear what the prime minister has to tell us.”