A MASSIVE urban expansion of Melbourne and higher density housing in existing suburbs - particularly along transport routes - now looks likely with government aiming to split opposition parties to get the planning changes through state parliament.

Planning Minister Justin Madden is expected to introduce two separate planning scheme amendments to Parliament at the end of the month, one enabling a 43,600-hectare expansion of Melbourne's boundary and another supporting higher density housing in existing suburbs - particularly along transport routes.

The Coalition Liberal and National parties are expected to support the urban boundary expansion amendment - the fate of the higher density housing amendment is less clear, with all opposition parties, including the Greens and Democratic Labor Party needing to unite to block the change.

The government failed last month to get the planning changes through Parliament in a combined planning scheme amendment with the Liberal and National Party Coalition opposed to the higher density housing in existing suburbs provision. Opposition planning spokesman Matthew Guy met Mr Madden yesterday and said the government's decision to enter the urban boundary changes separately was a massive backflip.

A spokeswoman for Mr Madden said it was ''incumbent on government to rise above partisan politics and deliver on the issues that matter''.