Junk food advertising should be banned from Victoria's public transport network to protect children, health and political groups warn.

The Victorian Greens have called on the state government to clamp down on unhealthy food and drink ads at train stations and tram stops.

Research from Cancer Council Victoria shows children in the state see or hear at least 25 ads promoting unhealthy food and drinks every day, negatively influencing their eating habits.

Greens population health spokesman Tim Read said the public transport network was one of the few areas where the state government has control over advertising.

"Processed food companies do not spend millions of dollars on outdoor advertising for fun," Dr Read told reporters at parliament.

"They spend millions of dollars on outdoor advertising so they can teach our kids what to eat and set them up to buy their products. The state can either go along with that, or it can take action."

Premier Daniel Andrews shot down the suggestion, questioning if banning google ads would be effective.

"I'm not looking to ban anything today. I don't know whether that necessarily works," he said.

"There's a thing called the internet. People get their information from lots of different sources."

Mr Andrews also expressed concerns about the potential loss of revenue from removing the ads, leaving the government with less cash to reinvest in the network.

Dr Reed conceded there could be some revenue implications, but said the Greens did not expect it to be a "major hit" to the state budget.

"When the City of London did this, they found, probably by coincidence, that their revenue actually went up," he said.

A spokesman for VicHealth, the state's health promotion foundation, said the impacts of limiting junk food advertising on London transport have been more than monetary.

"This (the ban) resulted in the average weekly household purchases of energy from chocolate and confectionery dropping 19 per cent following the changes," he told AAP.

"It's time to put the health and wellbeing of our kids first by removing this type of advertising around public transport, its infrastructure, and particularly schools."

Other Australian states and territories, including Western Australia, Queensland and the ACT, are implementing various measures to limit or eliminate junk food advertising from public spaces.