DUP leader Jeffrey Donaldson has said a meeting with Taoiseach Micheal Martin in Belfast on Friday was “useful” but added the party is not interested in “tinkering around the edges” on the protocol.
Sir Jeffrey said: "We have had what I would describe as a useful meeting with the Taoiseach, we spelled it out very clearly to him the problems with the protocol, the harm it is doing to Northern Ireland and that we need a solution, we need decisive action to deal with these problems.
"We are not interested in a sticking plaster approach, or tinkering around the edges, it has to be fundamental change which respects Northern Ireland's place within the UK internal market and nothing short of that will suffice."
Earlier, Mr Martin claimed the UK Government has moved “too far in a unilateral way on issues” and branded the DUP’s boycott of Stormont as “unheard of”.
Speaking ahead of her meeting with the Taoiseach, Sinn Fein vice president Michelle O'Neill accused the DUP of "denying democracy" by refusing to enter government in Northern Ireland.
On BBC NI’s Good Morning Ulster, Mr Martin criticised the current situation surrounding the Assembly, with the DUP having refused to allow the nomination of a Speaker at Stormont.
“Most people would agree that in the democratic world when people vote for their representatives and vote for a parliament the first thing that should happen is that parliament should convene,” he said.
“The Executive formed could have a say in terms of all of this.
“It is unheard of in the democratic that world a parliament would not convene in the aftermath of an election.
“We can’t have a situation where one political party determines the other political parties can’t convene in a parliament.
“The challenge I see here is the goalposts [from the UK] keep on changing in respect of the protocol. If you look at the Foreign Secretary’s speech this week, it is getting wider and wider on a range of issues.”
On the relationship between the Irish Government and British Government, Mr Martin said he believes the UK has moved “too far” in a “unilateral way” on issues such as legacy and the protocol.
“There will always be dialogue and engagement between the British Government and Irish Government. It has to be a very close relationship,” the Irish premier added.
“Be it legacy issues or the protocol. In my view that is not fully in accordance with the spirit of the Good Friday Agreement.”
Ms O’Neill said she “welcomed” the Taoiseach’s visit.
"He has a very significant role in terms of being the co-guarantor of our peace agreement and therefore has a stewardship role to play,” she added.
"At a time where democracy is being denied, at a time where the DUP are continuing to prevent the facilitation of an Executive being formed, an executive that could start to deliver for the public, I think it is important that he is here to assert his role and to listen to all of the parties.”
Meanwhile, Mr Donaldson responded to US congresswoman and House speaker Pelosi on the protocol, who said ensuring there is no “physical border” between Northern Ireland and the Republic “is absolutely necessary” for upholding the 1998 Good Friday Agreement.
Speaking on BBC NI, Mr Donaldson said Ms Pelosi has to “recognise it is the protocol undermining the agreement”.
“Nancy Pelosi states the reason she is concerned is because the Good Friday Agreement might be undermined but the protocol is undermining the agreement,” Mr Donaldson said.
“The protocol has changed some of the key principles of the Belfast Agreement. It has made it impossible to have power sharing on a cross community consensus.
“If Nancy Pelosi wants to see the agreement protected, then she has to recognise it is the protocol undermining the agreement. We will not re-enter the political institutions in full until we see decisive action on the protocol.”
The DUP is currently blocking the re-establishment of Stormont's power-sharing institutions in protest at the protocol, which has created economic barriers on trade between Great Britain and Northern Ireland.
Ulster Unionist Party leader Doug Beattie described Ms Pelosi’s intervention as “deeply regrettable and misinformed”.
“Nancy Pelosi`s comments will only lead to a hardening of positions rather than easing a pathway to solutions which is what all politicians should be concentrating on,” he said.
"Added to Simon Coveney`s comments this week saying that the peace process is under threat and now Leo Varadkar claiming that the Protocol is working, when it is plain for all to see that it is not, makes progress more difficult.”
Councillor Stephen Cooper from the TUV said both Mr Martin and Ms Pelosi have “no business lecturing Unionists on what they can and cannot do”.
“Whether it is Nancy Pelosi on Twitter or Dublin’s Prime Minister on a trip to Belfast the interference of foreign figures in what are internal U.K. matters is unwelcome and inappropriate,” he added.
The strongly-worded intervention by Ms Pelosi included a warning that any unilateral UK legislation affecting the Northern Ireland Protocol could endanger British prospects for a free trade deal with the United States.
"It is deeply concerning that the United Kingdom is now seeking to unilaterally discard the Northern Ireland Protocol. Negotiated agreements like the Protocol preserve the important progress and stability forged by the Good Friday Accords, which continue to enjoy strong bipartisan and bicameral support in the United States Congress," Ms Pelosi said.
"As I have stated in my conversations with the Prime Minister, the Foreign Secretary and Members of the House of Commons, if the United Kingdom chooses to undermine the Good Friday Accords, the Congress cannot and will not support a bilateral free trade agreement with the United Kingdom.
"Respectful of the will of the British people and of Brexit, I urge constructive, collaborative and good-faith negotiations to implement an agreement that upholds peace.
"The children of Northern Ireland, who have never known the bloody conflict and do not want to go back, deserve a future free of the violence where all may reach their fulfillment."