One of Hong Kong's top coronavirus experts has joined a growing chorus of criticism over plans to test the entire city, saying doing so during its worst-ever outbreak would have little impact, AFP reports.

The criticism from Yuen Kwok-yung, a veteran microbiologist who led the city's fight against SARS in 2003, follows multiple other local health experts taking issue with the strategy this week.

Yuen, a key government pandemic adviser, said mass testing can help break transmission chains when there are “only a few dozen or a few hundred cases a day” and has been deployed successfully in mainland China when outbreaks first emerge.

"If we are recording over 50,000 new cases every day, I don't think (mass testing) will be very helpful," he told reporters.