China has refused repeated requests by the World Health Organisation to take part in investigations into the origins of COVID-19, the WHO representative in China has told Sky News.

"We know that some national investigation is happening but at this stage we have not been invited to join," Dr Gauden Galea said.

"WHO is making requests of the health commission and of the authorities," he said. "The origins of virus are very important, the animal-human interface is extremely important and needs to be studied.

"The priority is we need to know as much as possible to prevent the reoccurrence."

Asked by Sky News whether there was a good reason not to include the WHO, Dr Galea replied: "From our point of view, no."

The Australian government has said that an independent public enquiry should be held into the origins of COVID-19, a measure EU countries are reportedly considering publicly endorsing.

China has reacted angrily, saying that the investigation into the virus should be a matter for scientists.

Dr Galea also told Sky News that the WHO had not been able to investigate logs from the two laboratories working with viruses in Wuhan, the Wuhan Institute of Virology and the Wuhan CDC.

"From all available evidence, WHO colleagues in our three-level system are convinced that the origins are in Wuhan and that it is a naturally occurring, not a manufactured, virus," he said.

Nevertheless, according to Dr Galea, the laboratory logs "would need to be part of any full report, any full look at the story of the origins".

Dr Galea defended the WHO's role in the early days of the novel coronavirus outbreak.

"We only know what China is reporting to us at that period in time."

From 3 January to 16 January, Wuhan officials reported no new coronavirus cases beyond the 41 already published.

"Is it likely that there were only 41 cases for that period of time? I would think not," Dr Galea told Sky News.

"Is that a matter of difficulty in finding were they getting their act together, is it a question of definition? I cannot speculate. But it would have been during that period obviously some growth would have been happening.

"It is unlikely that with an epidemic of this nature that it stays at 41 exactly.

"But yes, were there more cases? That is something that China will have to answer for."

The central question in the initial outbreak of the virus was whether it could be transmitted from human to human - a characteristic that would make it much more likely to spread widely than if infection relied on direct contamination from the original source, still thought to be the Huanan Seafood market in Wuhan.

The WHO has been criticised for a tweet it posted on 14 January, saying "Preliminary investigations conducted by the Chinese authorities have found no clear evidence of human-to-human transmission".

The same day, in Geneva, a WHO official said there had been "limited" human-to-human transmission.

Dr Galea told Sky News that, at the time, the "WHO was increasingly worried and convinced, suspecting strongly there would be human-to-human transmission. But as yet the cases that had been presented to us and the investigations had not yet confirmed that 100%."

That changed when the WHO China team was able to make a brief visit to Wuhan, from 20-21 January in an almost casual encounter.

"The healthcare worker simply volunteered the moment we entered the fever clinic," Dr Galea said.

"We were shown around at that point the makeshift system that had been set up and we simply asked it as one of the first questions. And immediately we got that answer. In that case they said they had had two cases, two healthcare workers that were infected."

On 20 January, China announced that the virus was transmissible human to human.

The WHO in China is now studying the country's current epidemic prevention, as the outbreak has been brought under control and lockdowns have been lifted.

But Dr Galea urged caution, especially about the prospects of a vaccine: "The fact that we don't yet have a vaccine [in production] for any coronavirus suggests that we should not be making plan A the fact that we're going to have a vaccine by such and such a date."