The UK Supreme Court has unanimously ruled that the Brexit Northern Ireland Protocol is lawful.

The legality of the contentious trading arrangements was challenged at the UK's highest court by a collective of unionists and Brexiteers.

The original appellants, including former Stormont first ministers Arlene Foster and the late David Trimble, had argued the arrangements were unlawful.

But the challenge was rejected by a panel of five justices yesterday, after a two-day hearing last year. It had previously also been dismissed by the High Court and Court of Appeal in Belfast.

Sinn Féin vice president Michelle O'Neill welcomed the court judgment and said there was no alternative to the protocol and that it needed to be made to work better for everyone.

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She tweeted: "I welcome the Supreme Court ruling which rejects arguments that the protocol is incompatible with the Good Friday Agreement. The protocol is lawful, but also necessary to limit the damage done by Brexit."

DUP leader Jeffrey Donaldson said the decision highlights why solutions to the contentious trading arrangements must be found by the British government. Mr Donaldson was at the Supreme Court yesterday to hear Judge Ben Stephens rule that the challenge was "unanimously dismissed" on all grounds.

Speaking afterwards, Mr Donaldson said: "A solution to the protocol was never going to be found in the courts, but the cases have served to highlight some of the reasons why unionists have uniformly rejected the protocol.

"The British government must consider this judgment, their own arguments to the court and take the steps necessary to replace the protocol with arrangements that unionists can support."

Image: Michelle O'Neill stands beside Arlene Foster (Getty)