It comes after 12,326 tests were conducted on Tuesday, taking the total number of tests over the past three days to more than 30,000.

The surge in testing, prompted by a hotel security guard who roamed the streets of Perth while infectious, paves the way for metropolitan Perth, the Peel region and South West to likely emerge from lockdown at 6pm on Friday.

"This is a very encouraging result, especially considering we are testing at record levels. But we are not out of the woods yet," Premier Mark McGowan said on Wednesday.

"I want the WA community to understand that if we do continue on a zero-case streak through to Friday, the lockdown will end ... but some form of restrictions will be necessary for the following week or so."

Questions remain unanswered about the breach at the Sheraton Four Points quarantine hotel, including whether the security guard behind the outbreak was wearing a mask when he delivered medication to a sick guest.

Contact tracers have identified 189 close contacts, 138 of whom have returned negative results.

Of a further 234 casual contacts, 116 have so far tested negative.

Mr McGowan said the guard's three housemates, who are in hotel quarantine, have been re-tested and their results are pending.

Fifty-four guests at the Sheraton who were due to finish their quarantine periods were held back so they could be re-tested as a precaution.

They have since returned negative tests and will be released later on Wednesday.

Health Minister Roger Cook on Tuesday revealed hotel quarantine guards were not expected to wear a mask at all times, even while on the same floor as confirmed COVID patients.

Opposition Leader Zak Kirkup has called on the government to enforce mask-wearing for such workers at all times within hotels.

In his most stringent comments since becoming leader of the Liberals late last year and pledging a unity ticket on the health response, Mr Kirkup on Wednesday accused the government of complacency in its handling of the pandemic.

"We have a five-day lockdown because the hotel quarantine system failed," he told reporters.

Mr Kirkup denied he was seeking to politicise the crisis ahead of the March 13 election, which the Labor government is predicted to comfortably win.

"Our unity ticket has always been to back in the chief health officer's advice and that doesn't change," he said.

Genomic testing has linked the guard's case to the same highly contagious UK variant present in two recently returned overseas travellers.

He is believed to have delivered medication to one of the travellers who was accommodated on the same floor on which he was working on January 24.

Mr Cook has said the government will review whether hotel security guards should be required to wear a mask at all times.

The family of the guard, a man in his 20s dubbed "case 903", has told The West Australian newspaper he has no serious symptoms but is distraught about having potentially infected others.

Authorities are yet to reveal what restrictions might remain in place beyond the lockdown, although schools are expected to return next Monday.

Australian Associated Press