As business-led fierce criticism of the plan released on Monday, Chief Health Officer Brett Sutton said there could be room to move on Melbourne's October 26 and November 23 target dates.

But he added September 28 is set in stone and Professor Sutton stressed the October and November dates would be brought forward if statistics justified it.

The day after Premier Daniel Andrews announced the long-awaited roadmap details, Victoria recorded another nine deaths.

That brings the state toll to 675 and the national figure to 762.

But new case numbers dropped to 41, their lowest since June 26.

With the fortnight average still hovering around 100, Prof Sutton said there would be no change to the September 28 milestone, when some Melbourne workplaces and schools will reopen if the average has dropped below 50.

"We need to absolutely have that time to drive transmission down so we're going in the right direction," Prof Sutton said of September 28.

If the fortnight average is less than five on October 26, and if there is also an average of less than five "mystery" cases, then Melbourne's curfew will end among other measures being eased.

Asked about October 26, Prof Sutton said: "We would always go through a process of review that we wouldn't say different circumstances shouldn't lead to a relook at how we're tracking and the risk of moving to a different stage.

"I think the clarity is important but ... everyone would welcome an earlier opening rather than a later one."

Then comes November 23, when all retail in Melbourne can reopen if there have been no new cases for the previous fortnight.

Also on Monday, Prime Minister Scott Morrison made it clear again the federal government is no fan of the roadmap schedule.

"The plan that was outlined yesterday, I hope, is a worst-case scenario," he said.

State opposition leader Michael O'Brien referenced a comment piece in The Age from Deakin University epidemiology expert Catherine Bennett, who questioned several of the assumptions underpinning the roadmap.

"We're going from the world's most liveable city to the world's most locked-down city," Mr O'Brien said.

Small Business and Family Enterprise Ombudsman Kate Carnell said owners are struggling under the weight of costs, including rent, equipment leases, loans and an accumulation of worker entitlements.

"What small businesses are telling us is that they are giving up," she told Nine's Today program on Monday.

"For many of them, they are not going to be open until the end of November."

She also called on the state government to cover the costs of small business closures.

But Mr Andrews staunchly defended the roadmap, rejecting criticism that the government did not listen to business concerns.

"That's not to say that business received the news that they wanted. But that's a different thing to not being listened to. I would reject that. That's simply wrong," he said.

He also noted that Victoria hit its peak of 725 new cases on August 5.

"We are having considerable success. We are bringing a sense of control to this," he said.

While Melbourne's stage four restrictions will remain for another fortnight, from September 14 the nightly curfew will start an hour later at 9pm.

People living alone will also be able to nominate a friend or family member who can visit, while two hours of daily exercise will be allowed, including social interactions such as picnics in parks.

But regional Victoria is on a different timetable and will be able to move to the third step of restrictions soon.

Australian Associated Press