Justice Samuel Alito, who wrote the ruling, dismissed criticism from a host of prominent figures, including UK Prime Minister Boris Johnson.

He joked that Johnson, who leaves office in September, had "paid the price" for arguing against the verdict.

Alito, a devout Catholic, was speaking at a conference in Rome.

"I had the honor this term of writing I think the only supreme court decision in the history of that institution that has been lambasted by a whole string of foreign leaders who felt perfectly fine commenting on American law," Alito said.

"One of these was Boris Johnson, but he paid the price," he said, drawing laughter from the audience. Johnson, who announced his intention to resign earlier this month after a string of scandals, had called the ruling "a big step backward".

Alito also referenced French President Emmanuel Macron, Canadian Prime Minister Justin Trudeau and the Duke of Sussex, Prince Harry, who had condemned the "rolling back of constitutional rights" in the US during a speech to the UN earlier this month.

"What really wounded me was when the Duke of Sussex addressed the United Nations and seemed to compare the decision whose name may not be spoken with the Russian attack on Ukraine," Alito said.

Prince Harry appeared to be referring to the abortion ruling when he said in his address to the UN: "From the horrific war in Ukraine to the rolling back of constitutional rights here in the United States, we are witnessing a global assault on democracy and freedom..."

Alito's previously unannounced speech was delivered to the Religious Liberty Conference on 21 July and emerged after the University of Notre Dame, who hosted the event, posted footage online on Thursday night.

Referring to religious liberty, he said it was "under attack in many places because it is dangerous to those who want to hold complete power".

Appointed to the court by President George W Bush in 2006, Alito made an intervention that is extremely unusual for a member of the Supreme Court. Justices of America's top court are usually expected to avoid wading into political debates.

Writing on Twitter, Democratic Congresswoman Alexandria Ocasio Cortez said the top judge's "politicized remarks" should be alarming to voters, adding that the "Supreme Court is in a legitimacy crisis".

Alito's intervention came on the same day as a liberal member of the court, Justice Elena Kagan, warned it would be a "dangerous thing for a democracy" if the court's conservative majority lost the confidence of voters.

"I'm not talking about any particular decision or even any particular series of decisions, but if over time the court loses all connection with the public and with public sentiment, that's a dangerous thing for a democracy," she said at a conference in Montana,

Opinion polls suggest that confidence in the court is at an all-time low in the wake of several controversial decisions by the court. Just 25% of those polled said they had confidence in the body.