BEIJING (REUTERS) - A senior Chinese health official said on Wednesday (March 31) that there was no factual basis to accusations that China did not share data with researchers appointed by the World Health Organisation (WHO) to look into the origins of Covid-19.

Following the official publication of the joint study into the origins of Covid-19 by China and the WHO on Tuesday, WHO director-general Tedros Adhanom Ghebreyesus said China had withheld data from international investigators during their visit to the central Chinese city of Wuhan, where the coronavirus was first identified.

But Dr Liang Wannian, who was co-leader of the joint study, told reporters that Chinese and international researchers had access to the same data throughout the investigation and that the claims about lack of access were not accurate.

"Of course, according to Chinese law, some data cannot be taken away or photographed, but when we were analysing it together in Wuhan, everyone could see the database, the materials - it was all done together," he said.

Dr Liang also rejected complaints that the publication of the report had been regularly delayed, noting that "every sentence, every conclusion, every piece of data" needed to be verified by both sides before it could be released.

"Throughout we always upheld the principle of 'quality comes first'," said Dr Liang, who is the head of a committee of experts on Covid-19 set up by China's National Health Commission.

Dr Liang also said the Chinese part of the joint research had been completed, and the world now needed to look further into potential early cases of Covid-19 outside China in the next phase of its research into the origins of the pandemic.