SYDNEY (AFP) - Australia will not join the growing list of nations banning British travellers, officials said on Monday (Dec 21), expressing doubts that Britain's latest infection surge was solely due to a new coronavirus strain.

Prime Minister Scott Morrison said Australia - which still shares a monarch with its former colonial power - was confident existing 14-day quarantine rules for arriving travellers were sufficient to handle the threat.

A slew of allies have moved to block planes, trains and vessels arriving from Britain, as London warned the spread of a new - seemingly more infectious - virus strain had surged "out of control".

Australia's acting chief medical officer Paul Kelly insisted people arriving from Britain were "no risk" to the Australian public because like almost everyone, they must undergo 14 days' strict quarantine when entering the country.

He also poured cold water on London's suggestion that a shocking uptick in infection rates was primarily caused by a new super-strain.

"I think we need to put that in context," Dr Kelly said, noting that "there have been thousands of mutations" of the coronavirus since it was first detected.

"There is no definite evidence at the moment that this is a significant change," he said.

British Prime Minister Boris Johnson had initially refused to recommend a lockdown over Christmas, despite rapidly rising case numbers.

His government has since made a U-turn, with Health Minister Matt Hancock blaming a new strain that was "out of control".

Australian health authorities say they have already detected the British strain in quarantined travellers.

But those cases are not said to be linked to a cluster of 83 cases in Sydney, which ended Australia's weeks-long run of no community transmission.

The authorities have responded with record levels of testing, as well as intense contact tracing efforts, local lockdowns and reimposed restrictions on mass gatherings.