Hong Kong is pushing forward with plans to change its laws to allow for the extradition of criminals to China for the first time, prompting widespread protests and fears for the territory’s judicial independence.

Proposed amendments to Hong Kong’s extradition were introduced at the city’s legislative council on Wednesday, after thousands of demonstrators took to the streets at the weekend.

The Hong Kong chief executive, Carrie Lam, defended the proposal, which would give her the power to order the transfer of suspects to China. Current Hong Kong law bars any renditions to China or other jurisdictions of the People’s Republic of China.

“If you are of the view there is no independent judiciary in Hong Kong … it is nonsense … You are insulting ourselves, because we have set up a very independent judiciary,” she said.

Democratic lawmakers shouted during the session and about 20 walked out, according to a legislative member who attended. The bill is expected to be put to a vote by July, when it is likely to be passed by the pro-Beijing-dominated legislature.

Under the terms of Hong Kong’s return to Chinese control in 1997, the former British colony is meant to enjoy a “high degree of autonomy” from the mainland, with its own judicial and legislative systems. Critics worry the proposed new extradition arrangement would further erode the city’s rule of law and independence.

The push to change the extradition law stems from the killing of a Hong Kong woman while on a Valentine’s trip with her boyfriend to Taiwan last year. The woman’s boyfriend, suspected of her murder, can only be tried in Taiwan. Because Hong Kong has no extradition agreement with Taiwan, he has remained in Hong Kong.

Those in support of the amendments say they will close such legal loopholes and protect Hong Kong from becoming a “paradise for criminals”. A spokesperson for China’s ministry of foreign affairs office in Hong Kong said last month: “Cooperation against crime is a common interest in the international community.”

But critics worry it will result in regular extradition requests from Beijing, which the pro-Beijing government would likely honour, according to critics.

Eric Cheung, a legal expert at the University of Hong Kong, said: “How can you expect our chief executive to say no when faced by the central government?”

Since the handover, Hong Kong has not allowed for the extradition of criminals or suspects to mainland China specifically because of the lack of legal protections for those tried in Chinese courts, according to the Hong Kong Bar Association, which opposes the amendments.

Arbitrary detentions, forced confessions, torture, detention without trial, the use of trumped up or vague charges, and the denial of lawyers of one’s choosing are common in China’s court system, where the conviction rate is often as high as 99%.

Cheung said: “There is no way the Hong Kong government or Hong Kong courts can ensure that the person extradited back to China can have a fair trial. How can we guarantee that the person will have access to lawyers? How can we ensure that this person will not be subject to violence or threats to coerce him to plead guilty?”

The arrangement could make it easier for Beijing to seek retribution for cases such as the arrest of the Huawei executive, Meng Wanzhou, in Canada, at the request of the US, according to Dennis Kwok, a lawmaker with the Civic party.

“What could be possible is that theChinese government will weaponise and use this system against foreign nationals doing business or passing through Hong Kong,” he said.

Business groups such as the American Chamber of Commerce have said the law will hurt the city’s attractiveness to foreign businesses and investors. Human rights groups and media advocates say it will affect the city’s freedom of speech, a privilege Hong Kong media enjoy that mainland media do not.

The Hong Kong Journalists Association said on Wednesday the changes would “not only threaten the safety of journalists but also have a chilling effect on the freedom of expression in Hong Kong”.