Cheung said on Tuesday the Hong Kong government had examined all available options before concluding that the best solution was to let Chan freely surrender himself to the self-governing island. But Taipei has said it will only accept Chan after formal mutual-assistance talks between both sides.

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“Rather than allowing political considerations to override the rule of law and justice, and complicating a simple matter, I hope Taiwan authorities can be pragmatic and proactive. When a wanted man wants to surrender himself, why insist on a mutual assistance agreement?” he said.

“Don't use politics, really, do not try to exploit politics in order to achieve certain gain at the expense, particularly, of justice.”

The official was speaking on Tuesday before chairing the Executive Council’s weekly meeting as acting city leader, with Chief Executive Carrie Lam Cheng Yuet-ngor on an official visit to Japan.

The extradition bill, which would have allowed transfers of fugitives to jurisdictions with which Hong Kong lacks a formal deal – including mainland China and Taiwan – was partly motivated by solving the Chan case, the government previously claimed.

The Hong Kong and Taiwan governments both toughened their stances on Monday, each demanding the other side’s cooperation in an escalating row over the man’s fate.

Taipei said Chan’s offer to surrender himself was not enough, and formal talks were required within a mutual legal assistance framework. The Hong Kong government countered that it was a simple matter of him turning himself in.

Cheung said on Tuesday he found it “incomprehensible” that Taiwan would refuse to accept Chan’s surrender, when Hong Kong has no jurisdiction over the case.

Asked if he was worried Chan would change his mind about surrendering himself, Cheung said: “I think his decision is clear, so we hope he can go to Taiwan as soon as possible.”

In Taiwan, President Tsai Ing-wen said it was the Hong Kong government who put politics before justice.

“It was clear who put politics before the law when it did not handle what it should handle. The Taiwan government is willing to take up its responsibility ... but the Hong Kong government must provide the necessary help, or the judicial authorities here will have no way to gather full and complete information and evidence,” she said.

“Since Hong Kong people visit many countries, and if similar things happen in other countries and Hong Kong continues to deal with the cases in such a manner, it would be a serious headache to other governments.”

Tsai also dismissed former president Ma Ying-jeou’s allegation that the Taiwanese government was trying to drop the island’s jurisdiction over the murder case.

Before a session of Taiwan’s Legislative Yuan on Tuesday morning, Premier Su Tseng-chang stressed that both sides had jurisdiction over the case, but Chan, being in a Hong Kong prison, was more “accessible” to Hong Kong and it was more convenient for the city’s government to deal with him, to avoid a “judicial vacuum and let a major suspect run around”.

If Hong Kong needs Taiwan’s help, Su reiterated, it must respond to his government’s demand for judicial cooperation.

“[Hong Kong] has totally ignored [us] in the past. Now it’s keeping the same attitude – of course China is behind it – and it’s trying to [use the case] to justify its extradition bill,” he told reporters.

Hong Kong, Taiwan clash over surrender of fugitive murder suspect

“We won’t fall into the trap. We’re still hoping the Hong Kong government will respond to its people’s demands and deal with the extradition bill [saga] properly, and not politicise this case.”

The Hong Kong Bar Association previously suggested that the city’s government consider amending the law to empower the court to handle overseas criminal cases involving Hong Kong suspects.

Asked on Tuesday if that was feasible, Cheung said: “The Department of Justice and the Security Bureau have examined thoroughly all possible options, and in fact [Chan’s surrender] is the best option available at the moment because the gentleman concerned is willing to go back to Taiwan.”

But Democratic Party lawmaker James To Kun-sun said the government should explain why the Bar Association’s proposal was not feasible.

To, who had just returned from Taiwan meeting officials on Monday, also urged the Hong Kong government to have formal discussions with Taiwanese authorities, to hand over evidence where possible.

To also noted that Chan’s confession to murder remained a key piece of evidence for any potential prosecution in Taiwan. He urged Hong Kong authorities to clarify if the document of Chan’s confession could be transferred, or relevant Hong Kong officers could appear in a Taiwanese court to give testimony.

Beijing loyalist Tam Yiu-chung, Hong Kong’s sole representative to the standing committee of the National People’s Congress, hit out at Taipei’s call for Chan’s transfer to be handled under a formal mutual legal assistance framework.

“I think [Taiwan] have complicated and politicised the problem,” Tam said in Beijing.

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Meanwhile, Cheung said the city’s security minister would formally announce the withdrawal of the extradition bill at a Legislative Council meeting on Wednesday.

The announcement had been expected to take place after Lam’s policy address on October 16, but was postponed after opposition pan-democrats protested, and forced the meeting’s adjournment.

Constitutional lawyer Hong Wei-shen said the Taiwanese authorities were concerned the issue could undermine the island’s sovereignty, which Tsai has called on the public to defend.

“This is partly because Taiwan’s multiple requests to allow mutual legal assistance were rejected, while suddenly a pastor declared that Chan would be willing to turn himself in,” Hong said.

“The worry is coupled with [the apprehension that] Hong Kong will not commit to further mutual legal assistance once the suspect gets on the plane.”

He said an effective way to alleviate the concern would be by letting Chan’s lawyers handle the case and reducing the government’s involvement.

Additional reporting by Sum Lok-kei and Joyce Ng