Labour leader Sir Keir Starmer has said that his party will vote against British government legislation that would give powers to ministers to override parts of the Northern Ireland Protocol.
Speaking in Belfast, the Labour leader said: "We will vote against the legislation the government is putting before parliament. We think it is the wrong approach.
"I'm not pretending there aren't issues and challenges with the protocol, of course there are.
"We have been listening to the political parties here, to communities, to business groups. I think those challenges can be overcome around the negotiating table with statecraft, with high levels of trust.
"It is that high level of trust that is missing with this prime minister and I think he is making a mistake by going down the route of legislation which will breach international law and, actually, I think, be an impediment to the negotiations that, in the end, are going to resolve these difficult issues."
Downing Street today confirmed legislation giving powers to ministers to override parts of the Northern Ireland Protocol will be introduced to the Commons on Monday.
A No 10 spokesman said: "The Bill has been agreed by the relevant cabinet committees and will be introduced to Parliament on Monday. We will alongside the Bill publish a summary of the legal advice."
Sir Keir is in Belfast today to meet some of Stormont’s political leaders amid a deepening row over post-Brexit trading arrangements for the north.
The Labour leader arrived this morning for discussions with Alliance leader Naomi Long, SDLP chief Colum Eastwood and acting Stormont speaker Alan Chambers in Belfast.
He held meetings with DUP leader Sir Jeffrey Donaldson and UUP head Doug Beattie in London earlier this week and met Sinn Féin president Mary Lou McDonald last night in Belfast.
He is also expected to meet US consul general Paul Narain and go on a walkabout in Belfast to view changes in the city since the Good Friday Agreement.
SDLP leader Colum Eastwood praised Sir Keir after their meeting at Stormont.
"It's actually quite refreshing to see have Keir here, in Dublin yesterday and Stormont today, actually having a grown-up in leadership in London engaging properly with political parties here and with the Irish government," he said.
"It's what's been missing, frankly, from this British government over the past number of years. What we've seen from Boris Johnson has been unilateral action on legacy.
"Now, on Monday, we're going to see unilateral action on the protocol, having had no conversations with parties here, no conversations with the Irish government, and just taking a wrecking ball to the progress that we've had.
"We saw a glimpse over the past couple of days of what Anglo-Irish relationships could be like. It isn't impossible to have proper relationships, it isn't impossible to deal with the problems that we face in issues of the past or issues around the protocol.
"All of those things can be dealt with by grown-ups sitting down in a room and having a conversation. If we haven't learned that over the last 20 years, then I don't know what we've been watching."
After meeting Sir Keir, Alliance Party leader Naomi Long said reform of the Stormont institutions was necessary to prevent single parties such as the DUP from being able to block the formation of a devolved executive.
"The issues with the protocol really do not justify the egregious breach of international law and international trust that the Government are now embarking on via legislation basically at the behest of the DUP," she said.
"If the government wants to take some legislation forward so that these institutions here can be restored and that they can do that on a stable footing, they should be looking to reform these institutions in legislation to ensure that no party can hold the institutions to ransom going forward."
Mrs Long added: "We believe it is crucial that these institutions are reformed, the public have had enough of stop-start government, they have had enough of the cycle of crisis and collapse and we need to put paid to that by changing our institutions to make them fit for purpose."
Sir Keir worked in Belfast when he was a human rights adviser to the Northern Ireland Policing Board between 2003 and 2007.
While in the city, along with shadow Northern Ireland secretary Peter Kyle, he is expected to call for compromise and negotiation to end the political deadlock over the return of the powersharing executive.
The Northern Ireland Protocol will also feature in discussions, with the British government proposing controversial legislation to override parts of the treaty.
In Dublin yesterday, the UK Opposition leader accused the Briitsh prime minister of taking a “wrecking ball” to relationships with the Republic and the EU with his controversial plan to unilaterally scrap aspects of the post-Brexit trading arrangement.
The contentious Government Bill is due to be tabled at Westminster on Monday.
Last night, Sinn Féin vice president Michelle O’Neill warned the British government against unilateral moves to override the protocol during an address to party members in Belfast.
Ms O’Neill said: “Boris Johnson knows that to gamble the protocol is to breach international law and to jeopardise the British government’s agreement with the EU on their withdrawal and future trading relationship, with colossal political and economic impact.
“The threat of unilateral action by the Tories to legislate and breach international law serves nobody’s interests, anywhere, at any time.”
At the same time, DUP leader Sir Jeffrey Donaldson was addressing a party meeting in Kilkeel, Co Down, where he said there is a “unity of purpose within unionism in relation to the Northern Ireland Protocol”.
He added: “Even opinion polls show that the vast majority of unionists support our stance that the protocol must be resolved before devolution can be restored.”
The DUP has refused to allow the powersharing Assembly to meet or an executive to be formed as part of its protest against the protocol, which has created a trade border in the Irish Sea.