Taoiseach Leo Varadkar has said it would not be acceptable for the Northern Ireland Assembly to have a veto over the so-called backstop to avoid a hard Border.
The British government published proposals which would see Stormont given the power to veto new EU rules if the backstop came into effect post-Brexit.
It came as British Prime Minister Theresa May desperately seeks to build support for her Brexit deal ahead of a Westminster vote on the Withdrawal Agreement next week.
But amid renewed chaos in the House of Commons, she suffered another setback when MPs backed an amendment that would force Mrs May to outline a ‘Plan B‘ for Brexit within three working days if, as is likely, her deal is voted down next Tuesday.
Her government‘s latest proposals on Northern Ireland were designed to allay concerns over the backstop but they have already been rejected by the DUP, who Mrs May‘s administration relies on to stay in power.
DUP MP Sammy Wilson was quick to dismiss the document published by the British government as “window-dressing” and a “meaningless piece of paper”, insisting the backstop “has to go”.
Meanwhile, Sinn Féin leader Mary Lou McDonald said British attempts to “placate” the DUP can‘t undermine the backstop.
The Northern Ireland Assembly collapsed almost two years ago after a row between Sinn Féin and the DUP.
Mr Varadkar, speaking in Ethiopia, said it would not be acceptable for Stormont to have a veto over conditions attached to the backstop.
He said the existing Irish protocol provides for an input by the assembly already. He added: “I don‘t think we could have a situation whereby the Northern Ireland Executive or Assembly had a veto power because that would essentially give one of the two communities a veto power over the other and that would create a difficulty.”
Mr Varadkar said the people of Northern Ireland want to avoid a hard Border which the current Brexit deal provides for.
Tánaiste Simon Coveney said it was a “very serious time in British politics” and the Irish Government was watching very closely. He said it was a matter for the British government to manage the process but added: “All we are asking for is that decisions are made on the basis of fact, not rumour or not emotion.”
He said decisions taken in Westminster over the next week matter not only for Britain but for Ireland and many other EU countries.
Meanwhile, there was more turmoil in Westminster in a dramatic first day of debate on Mrs May‘s Brexit plan.
Amid chaotic scenes in the chamber, MPs backed an amendment requiring the prime minister to come back to the Commons within three working days to set out her ‘Plan B‘ if the deal is rejected.
The original intention was she would have three weeks to devise a new plan. While Downing Street sources said Mrs May always intended to “respond quickly” if she fails to secure Commons support for the deal, rejection would be seen as another blow to her authority.
The UK government later accepted proposals which would give the Commons the power to reject both an extension to the Brexit transition period and the introduction of a backstop if no trade deal is secured by the end of 2020.
The package, tabled by former minister Hugo Swire, also places a legally binding commitment on the government to end the backstop arrangement within 12 months, and to seek assurances from the EU that it will seek to do the same.
It is likely to prompt an angry response in Brussels, which has repeatedly rejected efforts to put a time limit on the backstop.
The British government would remain under an international obligation to keep the Border open, and it is understood ministers would be expected to seek alternative arrangements, possibly involving the use of new technology, within the 12-month deadline.