Carrie Lam speaks at a press conference in Hong Kong on Tuesday. Anthony Wallace / AFP

The extradition bill that had sparked the Hong Kong's biggest crisis in decades is dead, announced its leader Carrie Lam on Tuesday.

She also admitted that government work on the legislation had been a "total failure," but critics weren't amused and accused her of playing with words.

The bill, which would allow people in Hong Kong to be sent to mainland China to face trial in courts controlled by the Communist Party, sparked huge and at times violent street protests and plunged the former British colony into turmoil.

In mid-June, Lam responded to protests that drew hundreds of thousands of people on to the streets by suspending the bill, but that did not stop demonstrations that shut government offices and brought parts of the financial centre to a standstill.

Her latest attempt to restore order did not satisfy many protesters who stood by demands that she completely withdraw the bill.

"There are still lingering doubts about the government's sincerity or worries whether the government will restart the process in the Legislative Council," Lam told reporters on Tuesday.

"So, I reiterate here, there is no such plan, the bill is dead." The government's work on the bill had been a "total failure", she said.

The bill triggered outrage across broad sections of Hong Kong society amid concerns it would threaten the much-cherished rule of law that underpins the city's international financial status.

Lawyers and rights groups say China's justice system is marked by torture, forced confessions and arbitrary detention, claims that Beijing denies.

Hong Kong returned to Chinese rule in 1997 with the promise of a high degree of autonomy, including an independent legal system and right to protest, but in recent years there has been growing concern about the erosion of those freedoms at the hands of Beijing.

Critics of the extradition bill fear Beijing could use it to crack down on dissent.

University students who have been out in force during the protests denounced Lam's comments.

"What we want is to completely withdraw the bill. She is playing word games," said Chan Wai Lam William, general officer of the Student Union of Chinese University of Hong Kong.

Demonstrators have also called for Lam to resign as Hong Kong chief executive, for an independent investigation into police actions against protesters, and for the government to abandon the description of a violent protest on June 12 as a riot.

"It is not a simple thing for CE (chief executive) to step down, and I myself still have the passion and undertaking to service Hong Kong people," Lam said when asked about the protesters' demands.

"I hope that Hong Kong society can give me and my team the opportunity and room to allow us to use our new governance style to response to people's demand in economy and in livelihood." China has called the protests an "undisguised challenge" to the "one country, two systems" model under which Hong Kong is ruled.