The main expansion, along the Hume Freeway in the north and past Caroline Springs in the west — will add new housing estates to what is already one of the world’s most sprawling metropolises.

New land zoned for development will include thousands of hectares previously protected as “green wedge” zones.

Planning experts and green groups have strongly criticised the plans, accusing the Government of abandoning its policy of urban containment and of turning over environmentally sensitive land to developers.

But building and property groups welcomed the changes.

The Government has also confirmed plans for massive transport changes in the west and north, with more than 200 properties to be compulsorily acquired to make way for an outer ring road and a regional rail plan designed to fit in with urban boundary changes.

To build the outer ring road, the Government will buy 152 properties along a corridor from Werribee to Mill Park. The road will not be built before 2020.

The Government plans to start building the $4.2 billion rail line within 10 weeks, and wants it finished by 2014, with two new train stations in the west at Wyndham Vale and Tarneit. The line will ultimately carry Geelong trains to Melbourne along a 14-kilometre diversion via Sunshine, instead of the existing more direct route. Public Transport Minister Lynne Kosky conceded the change would add “a few seconds” to Geelong train trips, but said it would “improve reliability incredibly”.

Opposition transport spokesman Terry Mulder said the extra time would blow out. “She must explain how many minutes more the weekday daily fast train between Geelong and Southern Cross will take,” he said.

Melburnians will have just 30 days to comment on the changes.

The Government plans to acquire 15,000 hectares of native grasslands and establish new reserves to offset the loss of 6918 hectares of grasslands to be given over to development. The reserves will involve the Government buying up to 140 properties and dozens of houses.

Green groups welcomed the reserves, but criticised the loss of green wedge areas. Giorgio De Nola, of the Western Plains North Green Wedge Group, said the Government had rushed the assessment of important environmental areas.

Matt Ruchel, executive director of the Victorian National Parks Association, said making new grassland reserves outside the growth area “does not excuse the potential loss of more than 6000 hectares of grasslands” to urban development.

Premier John Brumby said the growth boundary had to be extended because of Victoria’s huge population boom. “We are seeing 2000 people a week coming to our state,” he said.

Liberal planning spokesman Matthew Guy attacked the plans to charge a tax of up to $95,000 per hectare on land brought into the new growth area as “a greedy tax grab”.

Planning Minister Justin Madden said he anticipated the Government would collect $2 billion in growth areas taxes over the next 20 years. “That will pay for the infrastructure at the time these suburbs are developed,” he said.

The Housing Industry Association and the Property Council both welcomed the expansion of the urban growth boundary, but expressed disappointed it was being linked to growth areas taxes.

Architect Philip Goad, of Melbourne University, said the urban expansion went “against the spirit” of the planning blueprint Melbourne 2030. “If you don’t stop the sprawl, it goes on indefinitely.”

RMIT University Associate Professor Michael Buxton said the decision to move the urban growth was “a total breach of government planning policy”.