Victorian Premier Daniel Andrews and Chief Health Officer Brett Sutton have moved to clarify some of the rules around the new measure.

From this Sunday, Melburnians living alone and single parents with all their children under 18 can nominate one person to visit their home.

There have been growing concerns about the impact of Melbourne's stage-four lockdown on people living by themselves.

Mr Andrews said the nominated support person does not have to live alone.

Much like intimate partners, the nominated person can also travel more than 5km from their home and stay overnight.

But they must abide by Melbourne's curfew which will be extended an hour from 9pm to 5am under the city's 'first step' of the pathway unveiled on Sunday.

"The curfew does apply, but the 5km limit does not," Mr Andrews told reporters on Monday.

A "social bubble" also cannot be formed between someone from metropolitan Melbourne and regional Victoria.

It will not run in conjunction with the intimate partner arrangement, meaning people will have to choose between the two schemes.

The support person can bring their children with them to their single friend's property if they cannot be left unattended.

Professor Sutton said they could come over to either house.

But if the nominated person lives with other adults, they must be out of the house when the single person visits.

The "social bubble" system will operate on an honesty policy, with people unable to change their nominee through the first and second steps.

"You can never say that no one will exploit this," Prof Sutton said.

"You can never say that about anything in this regard, and we've still got people who are doing the wrong thing occasionally.

"But overwhelmingly, people are following the rules and I think people understand that it's a risk if you go beyond what these restrictions allow."

Australian Associated Press