There is an “overwhelming case” to send a multilateral mission to Wuhan to investigate the coronavirus’s origins and spread, the former British governor to Hong Kong has told Dominic Raab.

Chris Patten wrote to the foreign secretary this week to raise his concern about “two issues that will affect us and the rest of the world for some time to come”: the Chinese government’s initial cover-up of the outbreak, and how it has apparently taken advantage of the pandemic to “turn the screws on Hong Kong”.

Patten told Raab he was concerned to see China’s ambassador to the UK engaging in “wolf diplomacy” by denying there had been a cover-up about the origins and early spread of the virus and implying that “respected politicians” in the UK and abroad were “peddling lies and disinformation”.

He said there was an overwhelming case in support of “establishing as soon as possible a multilateral expert mission to Wuhan to find out exactly what happened there”.

“Since Chinese communists are adamant that they have nothing to hide, they would presumably welcome such an inquiry,” Patten wrote.

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A spokesperson for the Foreign Office said: “Coronavirus is a global challenge and it’s vital that countries come together to tackle this shared threat. The foreign secretary has been clear that, in time, we will need to learn lessons and ask rigorous questions about why this outbreak happened, why it couldn’t be stopped earlier and what can be done to prevent another outbreak in future. This is something that we will look at with all of our international partners.”

On Thursday a vice-foreign minister for China, Le Yucheng, said the government “resolutely opposes” an international investigation, which he said would be “politicised” and aimed at stigmatising China.

On Wednesday Britain’s ambassador to the US, Karen Pierce, backed calls by the US and Australia for an inquiry, but said containing the outbreak was the first priority and such inquiries would come later.

It came after the UK foreign affairs parliamentary committee asked the government whether it planned to “hold China accountable” by making representations at gatherings of WHO, G7, or G20 members.

In his letter, Patten said the pandemic raised questions about the breach of Chinese obligations to the international health regulations of 2005 and as a member of the World Health Organization.

“I want to make clear straight away that Britain and other countries should have no argument with China and the Chinese people,” he said, praising the medical staff who fought the virus from the early stages.

“The issue is not our relationship with China. It is our relationship with the dangerous and immoral Communist party. In Wuhan the Communist party used the police to try and shut the doctors up. Totalitarian regimes always rely on secrecy and mendacity.”

Patten also urged Britain to step in on the deteriorating political situation in Hong Kong, where Beijing representatives and supporters have alarmed observers with intrusions on the city’s semi-autonomy.

Beijing’s top organisations in the region, the Hong Kong and Macau Affairs Office and the liaison office, recently weighed into domestic political arguments, drawing accusations they were acting in contravention to Hong Kong’s mini constitution, the Basic Law.

In response, authorities claimed the law did not apply to those offices, sparking furious condemnation from defenders of Hong Kong’s democracy. Authorities have also increased their crackdown on protesters, arresting 15 senior leaders of the democracy movement.

Patten said China had “taken advantage of the fact the international community is understandably focused on fighting the pandemic in order to turn the screws on Hong Kong”.

He said the statements about the Basic Law were a “flagrant breach of the joint declaration” signed by Britain and China when Hong Kong was handed over to the latter in 1997. Patten was part of the declaration negotiations, and has previously lobbied the UK government over Chinese intrusions on it.

“[Beijing officials] claim the right to call all the shots in Hong Kong thus destroying once and for all the promises that Hong Kong would have a high degree of local autonomy,” said Patten.

“They seem intent on destroying Deng Xiaoping’s concept of ‘one country, two systems’.”

Patten asked for assurances the government would press for a mission to Wuhan and would “call out China for its breaches of the joint declaration”, and watch for attempts to undermine Hong Kong’s rule of law or corrupt the electoral process.