A former leading UK judge has launched an unprecedented attack on the US Supreme Court, claiming its “legitimacy has been gravely undermined” by being so politically partisan.

Lord Sumption, a former UK Supreme Court judge, said the conservative majority on the US court had consistently backed Republican positions on abortion, gun control, election expenses, discriminatory voting rules, gerrymandering and the powers of agencies such as the Environmental Protection Agency.

“As a result, the court’s legitimacy has been gravely undermined and its public approval rating has collapsed from 80 per cent in the 1990s to less than 50 per cent now,” he wrote in an essay for Prospect magazine published on Wednesday.

He added: “This is a more serious problem in the United States than it would be in any other country. Congress is polarised, dysfunctional and gridlocked. Filibusters make it difficult to get controversial legislation through.

“When the Supreme Court changes the law on constitutional grounds there is no democratic way to undo it. Their rulings determine what the Constitution means until the crack of doom”.

Lord Sumption has also been a staunch critic of the European Convention on Human Rights and has urged the UK to leave the international agreement because he does not believe its “arrogant” court can change.

He said the Strasbourg-based court had become a “law-making factory” that had over-reached its powers, intruding into every aspect of people’s lives without a democratic mandate.

Lord Sumption was also a critic of the Covid lockdowns and accused the previous government of behaving like an authoritarian regime relying on police state tactics. 

It is the first time, however, that he has taken aim at the US Supreme Court.