Responding to allegations that the expert panel did not have access to complete datasets and samples, Liang Wannian said no scientist ever had perfect information.
A top Chinese medical expert said on Wednesday there was no factual basis to accusations that China did not share data with international researchers appointed by the World Health Organization to look into the origins of COVID
Following the 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 the international investigators.
But Liang Wannian, who was co-leader of the joint study, told reporters that researchers from both sides had access to the same data throughout the investigation and that the assertions 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.
Responding to allegations that the expert panel did not have access to complete datasets and samples, Liang said no scientist ever had perfect information.
He also rejected complaints that the publication of the report had been repeatedly 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 Liang, who is the head of a committee of experts on COVID
-19 set up by China's National Health Commission.
The joint study concluded that the most likely origin of COVID
-19 was in animals, and probably passed through an intermediary species before it entered humans.
It also said more efforts were needed to see if COVID
-19 could be traced back to wildlife farms in both China and southeast Asia.
Liang said China would continue to try to trace the origins of COVID
-19, but the Chinese part of the joint research had been completed, and attention should now turn to other countries.
Tracing the origins of COVID
-19 couldn't be achieved overnight, he said.
"There are lots of diseases that have circulated for a long time and we still haven't found their origins," he said. "It still needs a lot of time."