Chief Executive John Lee said on Tuesday a judge's professional duty is to interpret and apply the law, and that his or her expertise is not on politics.

Lee also said a departing non-permanent judge, Lord Jonathan Sumption, had contradicted his earlier comments with an opinion piece in the Financial Times.

Lord Sumption, who recently resigned as a judge on the Court of Final Appeal, wrote an article in the British newspaper titled "The rule of law in Hong Kong is in grave danger".

Ahead of the weekly Executive Council meeting, Lee said the overseas judge had expressed different views a few years ago.

"In 2021, Lord Sumption refused to take part in a political boycott orchestrated in the UK. And he said then that people should not confuse the rule of law with democracy," he said.

"His latest statement indicates that he doesn't like the political situation in Hong Kong. But this is exactly the area he has told us in 2021 that should not be confused with the rule of law. His recent statement looks to me to be contradictory to his previous stance in this regard."

The chief executive said judges should focus on handling legal matters.

"Judges' professional expertise is on law, based on his legal knowledge and experience. Judges' professional expertise is not on politics," he said.

"A judge is entitled to his personal political preferences, but that is not a judge's area of professional expertise.

"A judge can like a particular system or dislike it. He may also like a particular law or not. But his professional duty is to interpret and apply that particular piece of law in accordance with legal principles and evidence."

Lee also hit out at overseas efforts to attack the rule of law, saying that non-interference in the judicial process is "the DNA of Hong Kong's rule of law".