British Prime Minister Boris Johnson says he does not believe the COVID-19 virus escaped from a Chinese lab in Wuhan province but is keeping an eye on new evidence as it emerges.

"I've got an open mind on this, but I'll be clear with you — so far, the stuff I've seen does not suggest that the ... number one candidate for this is a lab leak," Johnson told CBC News chief political correspondent Rosemary Barton in an exclusive Canadian interview airing Sunday on Rosemary Barton Live.

"So the stuff I've seen suggests that at the moment, the number one suspect for the origin of this disease is still a zoonotic disease that occurred as a result of the farming of wild animals in some way."

Johnson said that while the theory that the virus came from the slaughter of wild animals is shared by British epidemiologists and the World Health Organization, he is "not going to exclude any possibility."

"I'm reading a lot of interesting stuff at the moment about the possibility that there was some, you know, virus escaping from a lab. I think we've got to keep an open mind," he told host Rosemary Barton.

Johnson spoke to CBC in advance of the G7 meeting being hosted by the British government next month in St Ives, Cornwall in the southwest of England.

Prime Minister Justin Trudeau will be attending the meeting in person, a Downing Street spokesperson told CBC News.

The controversial theory that COVID-19 came from a lab in Wuhan, China — where the Wuhan Institute of Virology studies the coronavirus in bats — emerged early on in the pandemic.

Former U.S. president Donald Trump backed the theory and called COVID-19 the "China virus." It was largely dismissed by the media, experts and the president's critics.

That position is swiftly changing, in part, because of a declassified U.S. intelligence report, made public earlier this month, that says several Chinese researchers at the institute became ill in November of 2019 and had to be hospitalized.

Anthony Fauci, the White House coronavirus adviser, told a Senate hearing last week that he and most others in the scientific community "believe that the most likely scenario is that this was a natural occurrence, but no one knows that 100 per cent for sure.

"Since there's a lot of concern, a lot of speculation and since no one absolutely knows that, I believe we do need the kind of investigation where there's open transparency and all the information that's available, to be made available, to scrutinize."

This week, U.S. President Joe Biden ordered intelligence officials to "redouble" their efforts to investigate the origins of the COVID-19 pandemic, including the possibility the trail might lead to a Chinese laboratory.

Biden told intelligence agencies to report back within 90 days and directed U.S. national laboratories to assist with the investigation and the intelligence community to prepare a list of specific queries for the Chinese government.

This week, Trudeau said his government supports the U.S. investigation to ensure accountability and to help prepare Canada for future pandemics.

"I know there are a lot of theories out there, but we need to make sure we're getting to a full and complete airing of the facts to actually understand what happened and how to make sure it never happens again," Trudeau said.

As a part of that preparation, Johnson said that the G7 meetings will include a discussion of how countries around the world could work to establish "zoonotic research hubs" to help determine where new animal-to-human diseases are emerging.