The State Government says the development of six new suburbs in Melbourne's fringe will be planned with adequate infrastructure.

The new suburbs will be developed at Diggers Rest, Lockerbie, Lockerbie North, Manor Lakes, Merrifield West and Rockbank North - all in Melbourne's outer north and west.

Over the next 30 years, 37,000 plots of land will be released and are expected to become home to more than 100,000 people.

Opposition planning spokesman Brian Tee says it could create a suburban nightmare without proper planning for transport, schools and other infrastructure.

"This is a recipe for chaos on our roads," he said.

But Planning Minister Matthew Guy says the new suburbs will be well planned.

"We are planning growth in transport and infrastructure," he said.

"There is also an announcement today in relation to moving that boundary into areas, some of it which is farmland, some of which is green wedge land.

"But it should be noted these are within growth areas."

He says developing the urban fringe provides more options for people who are priced out of the city.

Environmental groups say the State Government should have consulted the community before expanding into farming and green wedge land.

Rosemary West from the Green Wedges Coalition says Melburnians do not want to lose valuable wetlands and farms to development.

"We would hope that they have a rethink and ask people what they think," she said.

"Every survey that's ever been held on green wedges comes out with vast majorities wanting them protected."