Campaigners called for Robert Buckland to stand down over claims the government had broken international law.

Protesters gathered outside the Justice Secretary and South Swindon MP’s constituency office in Wood Street armed with signs calling the barrister a “law breaker” and signing a pastiche of the song “Rule Britannia” with the refrain “Fool Britannia, Britannia waives the rules”.

Liz Webster, Lib Dem candidate for Wiltshire police and crime commissioner role, said: “He should resign and do the right thing. This isn’t a small thing. It’s international law.”

In 2011, Mr Buckland was rapped by the Council of the Inns of Court for requesting case papers in the prosecution of a Ridgeway School student who attacked Mrs Webster’s son, Henry, with a hammer. Ms Webster campaigned at the time for a case review.

Nine years on, she told the Adver: “He’s now in charge of the law for the whole country at a very difficult time in a pandemic in my view he’s just once again more interested in protecting his own party and position rather than upholding international law, which threatens our reputation internationally.”

Speaking in front of a coffin-shaped placard marked “RIP UK law, Good Friday Agreement”, Steve Rouse of campaign group Swindon for Europe said at Monday night’s protest: “Many are calling for him to resign. What will it take for him to resign? If he believes in the law and he went along with the statement that it was a fantastic deal and you can trust us and vote for us, he should [now] resign.

“He seems to change tack with the wind. He seems to be able to bend himself to anything.”

The protest follows claims – acknowledged by the government – that the new Internal Markets Bill threatens to overturn the Brexit withdrawal agreement.

The bill, with amendments due to be voted on by MPs yesterday, is meant to ensure goods and services can pass freely between the UK nations after the country leaves the EU single market at the start of 2021. The legislation would give ministers powers to change parts of the withdrawal agreement.

Earlier this month, Northern Ireland Secretary Brandon Lewis admitted the new bill would break international law, as it would go against the treaty agreed with the EU in a “specific and limited way”.

However, under questioning from shadow Justice Secretary David Lammy yesterday, Mr Buckland told MPs: “Every member of the government is obliged to follow the rule of law, it’s very clear, I take a particular oath to uphold that and defend the judiciary.

“I have absolutely no qualms with what has been happening.

“I have worked extremely hard to make sure this House is fully involved, and I say to him that the idea this, the passage of this Bill, is a breach of UK domestic law is just plain wrong.”

Mr Buckland's representatives were contacted and offered the opportunity to comment on the campaigner’s claims.