LONDON — British lawmakers on Wednesday voted overwhelmingly in favor of a key component of a long-awaited deal on Northern Ireland trade rules, an emphatic victory for Prime Minister Rishi Sunak as he tries to resolve one of the most vexing legacies of Britain’s exit from the European Union.
Despite the strong backing of the agreement, the leading unionist party in the North, which seeks to remain part of the United Kingdom, said that it did not accept the deal and would refuse to form a local government, signaling more political turmoil ahead.
Several prominent members of the governing Conservative Party also broke ranks with the government and voted against the part of the deal that was under debate, including Boris Johnson and Liz Truss, two former prime ministers. Nonetheless, the measure passed in a landslide, 515 to 29.
The vote on Wednesday was on just one element of the agreement, known as the Stormont Brake, which would allow Northern Ireland to block the implementation of any “significantly different” new European rules on goods. The measure was aimed at addressing the North’s concerns that Brussels would have too much control over its trade rules. But the leading unionist party, the D.U.P., rejected the Stormont Brake as insufficient.
The lopsided nature of the vote was good news for Mr. Sunak, who has championed the broader trade deal, known as the Windsor Framework, that was negotiated with the European Union last month.
The vote on the Stormont Brake on Wednesday was the first time that British lawmakers had had a chance to weigh in on the deal, so it had been seen as a measure of their approval.
The D.U.P. said this week that it would not vote for the Windsor Framework agreement, and, as the vote on the Stormont Brake approached, its leaders confirmed that they had no plans either to enter into a power-sharing government in Northern Ireland’s devolved local assembly, known as Stormont. Northern Ireland’s other largest parties, including a different unionist party, have said that they support the framework.
“I have consistently indicated that fundamental problems remain notwithstanding progress made,” Jeffrey Donaldson, the leader of the D.U.P., said in a post on Twitter before the vote. “Consequently there is not a sustainable basis at this stage to enable us to restore Stormont.”
Speaking in Parliament a short time later, Mr. Donaldson said his party believed that the Windsor Framework agreement harmed Northern Ireland’s standing in the internal market of the United Kingdom, but he noted that he was willing to work with the government on “outstanding issues,” adding, “We’ve got to get it right.”
The British government has made it clear there are no plans for substantial changes.
