Hong Kong's outgoing top judge made a plea on Tuesday to maintain judicial independence as China state media and a growing host of pro-Beijing figures call for an overhaul of how the financial hub's courts are run.

Semi-autonomous Hong Kong owes much of its business success to a transparent and internationally respected common law legal system that stands in stark contrast with the opaque, party-controlled courts in authoritarian China.

But that system has come under sustained pressure in the politically charged wake of 2019's huge pro-democracy protests and Beijing's subsequent crackdown.

Last year Beijing began asserting more direct control over the city, including imposing a sweeping national security law that silenced dissent and dented the legal firewall between the business hub and the mainland.

Senior Chinese politicians, state media outlets as well as leading pro-Beijing figures and newspapers within Hong Kong have also lobbied for reforming the judiciary or criticised recent judgments and sentences they dislike.

Opponents fear those calls could presage the arrival of a legal system more akin to the authoritarian mainland.

On Tuesday, Hong Kong's chief justice Geoffrey Ma, 64, addressed those concerns at a final press conference ahead of his retirement.

"What we need most is judicial independence in Hong Kong," he said.

"There are three articles in the Basic Law emphasising that Hong Kong has judicial independence, this is what we should remember the most," he added, referencing the city's mini-constitution.

Ma was born in Hong Kong and educated in Britain
Ma was born in Hong Kong and educated in Britain AFP / Peter PARKS

Ma, who was born in Hong Kong and educated in Britain, said the judiciary was open to reform if it meant improving what they do.

"But it is not particularly satisfactory to call for reform on the basis of a result one does not like. It is certainly not a good starting point or acceptable that I want reforms to ensure I always get the result which I want," he added.

Judges have found themselves in the firing line of Hong Kong's polarised politics, including some who had private details leaked online, known as doxxing.

Both democracy supporters and government loyalists have criticised decisions they dislike but calls to overhaul the judiciary have so far only come from pro-Beijing figures.

In the most recent example, last month Beijing's communist party mouthpiece People's Daily newspaper published a scathing critique of a Hong Kong judge's decision to grant bail to Jimmy Lai, a pro-democracy media tycoon who was later remanded back into custody by a more senior court.

Ma said he faced no direct interference by Beijing or Hong Kong's government during his ten years as the city's top judge.

Criticism of judges, he ceded, had peaked last year prompting his office to issue an "unprecedented" number of statements.

But he rejected concerns that such pressure would impact the impartiality of judges.

"In the handling of cases, judges are going to look only at the law, legal principle and the spirit of the law," he said.

Ma will be succeeded by Andrew Cheung, a fellow permanent judge on the Court of Final Appeal.