THE DUP and Sinn Féin have rejected reported proposals from the British government to devolve more powers to Stormont in a bid to avoid a hard border after Brexit.
DUP MP Sammy Wilson warned that his party would end its agreement to support the Tory government at Westminster if any Brexit deal treats Northern Ireland differently from Britain.
And Sinn Féin deputy leader Mary Lou McDonald said the suggested plan "misses the point".
It follows reports of proposals to give Northern Ireland new powers to enable "customs convergence" with the Republic in areas such as agriculture and energy.
According to The Times, sources in Dublin said there had been "movement" on the border issue and confidence was growing that agreement could be reached before a crunch Brussels summit in a fortnight's time.
Northern Ireland has been without a devolved government since the start of the year after the DUP and Sinn Féin's power-sharing executive collapsed.
The British government's Department for Exiting the EU (DExEU) refused to comment on the newspaper report.
But Mr Wilson said his party will be "making clear to the government we have a confidence-and-supply arrangement with them", under which the minority Conservative administration relies on the support of the 10 DUP MPs to ensure its survival.
"If there is any hint that in order to placate Dublin and the EU, they're prepared to have Northern Ireland treated differently than the rest of the UK, then they can't rely on our vote," the East Antrim MP told the BBC.
"They have to recognise that if this is about treating Northern Ireland differently, or leaving us half in the EU, dragging along behind regulations which change in Dublin, it's not on."
Ms McDonald said: "All the talk about regulatory divergence and convergence misses the point.
"The solution is for the north to be granted designated special status within the European Union as part of any final agreement. That would allow the north to remain part of the single market and the customs union."
She added: "It is vital that the Irish government must secure clarity and binding agreements. Without this, the process should not be allowed to progress.
"Any talk of a parallel process is nonsense and dangerous at that. The time to defend Irish interests is now. So, the government must exercise its veto if necessary."
Pressure has mounted for the UK to agree a special arrangement under which Northern Ireland would continue to observe the rules of the EU's customs union to avoid a hard border with the Republic.
British prime minister Theresa May wants EU leaders at the European Council summit on December 14-15 to agree to move towards the second phase of Brexit negotiations – discussions on a future free trade deal.
But the Republic says to support this it needs commitments on the border.
The leaders of the remaining 27 EU states, including taoiseach Leo Varadkar, have a veto on triggering the second stage of talks, meaning Mrs May must be sure of support from Dublin.
Alliance's Stephen Farry welcomed the reported proposals, saying "regulatory convergence on the island could be one key component of some form of pragmatic way forward".
Ulster Unionist MEP Jim Nicholson said "none of us want a hard border with the Republic of Ireland" but the "answer is not to create a new border within the United Kingdom".
