WA's Chief Health Officer has wound back suggestions the state could open to much of the country, saying its hard border needs to remain in place for now.

Andrew Robertson's latest advice to the State Government said the situation in Victoria remained concerning, and border restrictions in place between that state and New South Wales and South Australia were unlikely to stop the virus spreading between the jurisdictions.

He said because of that, WA's border should remain closed, but should be reviewed again as scheduled in two weeks' time.

Dr Robertson's advice said Victoria's outbreak was expected to take up to two months to control.

"Victoria has now started to ease its lockdown in these areas and other states and territories are reviewing their border measures with Victoria, but given the current size of this outbreak, it is anticipated that it may take a further 1-2 months to get this fully under control," he said.

It is a step back from comments Dr Robertson made to a parliamentary committee yesterday.

He told the committee WA could open its border to most states around the country as they already met health requirements and had their own "generally" satisfactory border controls in place.

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Dr Robertson had previously said travel bubbles with states that had achieved 28 days without community transmission had always been under consideration.

He told the committee yesterday that was "certainly" still the case including with South Australia, Tasmania, the Northern Territory, the ACT and Queensland.

"We could consider removing quarantine requirements for states that have no community spread … that would be dependent on our confidence in the border arrangements with those states," he said.

Outside of the public hearings, Dr Robertson said he was "generally satisfied" with the border arrangements of most states.

"Many of them duplicate ours," he said.

But he said unsatisfactory border arrangements could lead to "border hopping", where people move rapidly through states to WA, passing through jurisdictions still experiencing COVID-19.

Questioning advice impugns CHO's integrity: Premier

The two pages of health advice provided today said the measures WA had in place "to control importation from Victoria remain appropriate and proportionate and are likely to remain so for at least a further two to four weeks".

"The trend in case numbers, however, should be reviewed in four weeks, and if cases have fallen to less than 5 cases per day over a five-day average, the exemptions currently in place for other jurisdictions should be considered," Dr Robertson said.

It also revealed community cases in NSW were expected to fall to less than five per day in the next two weeks.

"The border controls are considered appropriate and proportionate at this time, but it is recommended that they be reviewed in four weeks, particularly if they have less than 5 community cases per day," Dr Robertson said.

Premier Mark McGowan said Dr Robertson's latest advice, which he received this morning, reiterated the need for keeping the border closed.

"That is the confirmed position by the Chief Health Officer and if you want to question that, that means you're impugning his integrity, and you're also impugning the integrity of the Commissioner of Police, who has been working with him in implementing these matters," he said.

"And implementing these things is not easy … which is what the CO was talking about yesterday, implementation of all of these matters is difficult and is hard and people are doing a good job.

"The written advice is there for the whole world to see, the whole way along that we have followed the health advice and this Government … despite the Liberal Party has kept Western Australians safe."

Government 'cherry picking' advice, Opposition says

WA's Opposition has launched a scathing attack on Mr McGowan, accusing him of misleading the public over the health advice.

Liberal leader Liza Harvey claimed Dr Robertson's evidence yesterday revealed the Government was "cherry picking" from the advice for "political advantage".

"If you had been tabling the advice from the get go, none of this would have happened, because everyone in the community would know that there were a series of options available," she told Parliament.

"Options that you chose to ignore because you wanted to go with what you thought was the politically popular option, and the border closures are politically popular but they are not based on the health advice of the Chief Officer. And that's what you told people repeatedly."

The McGowan Government's position is there has to be 28 consecutive days of no community spread of the virus anywhere in the nation before the border can be opened, saying opening to some states and not others would be unconstitutional.

Ms Harvey said the Premier was "wallowing in self-adulation" but should apologise to the people of WA.

"This goes to the heart of your integrity and your character," she said.

"You need to apologise to the families who have missed births, the families who have missed weddings … the families who've missed going to funerals. You have significantly breached their trust."