DUP leader Sir Jeffrey Donaldson said he had told Irish Prime Minister Micheal Martin he was not interested in a ‘band-aid’ approach to solving problems with the Northern Ireland protocol.
The Taoiseach is in Belfast to meet party leaders amid the current standoff in Stormont over post-Brexit trade deals.
The Taoiseach is also meeting a series of business representatives during a visit which will be dominated by the political crisis over the controversial protocol.
The region’s main unionist party, the DUP, is currently blocking the restoration of power-sharing institutions in Stormont in protest at the protocol, which has created economic barriers to trade between Britain and Northern Ireland.
Following his meeting with the Taoiseach, Sir Jeffrey said: “We have made it very clear to him the problems with protocol, the harm it is doing to Northern Ireland and that we need a solution, we need decisive action to address these issues.
“We are not interested in a sticky plaster or tinkering around the edges approach, this needs to be a fundamental change that respects Northern Ireland’s place within the UK internal market and nothing less than that won’t be enough.”
The Taoiseach’s visit follows the British government’s controversial decision to act unilaterally to remove parts of the protocol.
Liz Truss announced on Tuesday that she intends to legislate to overturn parts of the Brexit withdrawal treaty with the EU.
Sir Jeffrey said he wanted to see the UK government publish its plans before making a decision on his reinstatement in political institutions.
He said: ‘I understand the government will introduce the legislation in early June.
“We will note what the legislation says and we will make decisions based on progress.
“I want the institutions working as soon as possible but I’m not going to telegram the government what I’m going to do until we see what this legislation says, it’s fundamentally important.
“I want the people of Northern Ireland to see what the government is proposing to do, which is why publishing the legislation is important and once we have seen this legislation we will of course consider what our next step will be. .”
Speaking earlier, Mr Martin had accused the UK government of going ‘one-sidedly too far’ on the protocol.
He told the BBC: ‘I’ve spoken to Boris Johnson and I have to understand this, this idea that the European Union is somehow inflexible about this is just not the truth, it doesn’t add up .
“What has happened now is a certain unilateralism from the British government saying ‘our way or not’ and you are not negotiating with the European Union on that basis, especially when you signed the okay you don’t like.
“Professional and serious negotiations between the UK government and the European Union are the only way to resolve this issue.
“I believe the current UK government has gone too far unilaterally on issues, whether it’s legacy, whether it’s protocol.
“In my view, this is not fully in line with the spirit of the Good Friday Agreement which involves collaboration, teamwork.”
Mr Martin also said there can be no situation where a political party refuses to allow the Northern Ireland Assembly to meet.
He added: “I think most people would agree that in the democratic world, when people vote for their representatives and vote to elect a parliament, the first thing that happens is for the parliament to meet.
“It is unheard of in a democratic world that this Parliament does not meet following an election.
“We cannot have a situation where one political party determines that other political parties cannot meet in a parliament.”
Mr Martin has also held meetings with Sinn Fein and Ulster Unionists, and will meet the SDLP later.
Sinn Fein Vice President Michelle O’Neill has accused the DUP of “denying democracy” by refusing to enter government in Northern Ireland.
Ms O’Neill said: ‘At a time when democracy is denied, at a time when the DUP continues to prevent the formation of an executive, an executive who could begin to serve the public, I think it is important that he is there to assert his role and listen to all the parties.
“There are parties here who want to be together in government, there are parties who want to be in the executive but unfortunately the DUP, sponsored by the British government, is holding back all that progress and preventing us from being able to start putting money in people’s pockets.
UUP leader Doug Beattie said reviving the Stormont executive could be a long process, but said the Assembly could restart in a limited way in a shorter timeframe.
“I have the impression that this legislation, this unilateral action will probably be brought before Parliament in the first two weeks of June, and that may be enough for a speaker (Stormont) to be appointed then, and that allows us to do limited work … and what happens after that will depend on whether or not the DUP can get the executive up and running,” he said.
“It could be a long process to get the executive in place, but we could manage it in a short time to at least get the assembly moving next month, maybe two months.
“I have nothing to suggest that is the case, it does not belong to me, it belongs to the Democratic Unionist Party.”
SDLP leader Colum Eastwood said it was not “sustainable” for the DUP to wait for the UK government to legislate on the protocol before entering the power-sharing executive.
Mr Eastwood said: ‘It could take several months for this legislation to actually be enacted, so is Jeffrey suggesting we wait until this is complete?
“Because people are going to wait month after month, after month, for a government to be formed and for action to be taken.
“It’s not a sustainable position in my view.”
Meanwhile, Irish Foreign Minister Simon Coveney met with Foreign Secretary Liz Truss over continuing concerns over the protocol.
He tweeted: “I have made clear Ireland’s opposition to the UK breaching international law.
“The UK must resume talks with the EU.”