There are large public transport black spots in Melbourne's rapidly growing outer suburbs, new research shows.

BusVic estimates 34,000 housing lots developed between 2004 and 2009 are still without public transport within walking distance - defined as 400 metres from a bus or tram route or 800 metres from a railway station.

Added to them are another 21,000 lots which were expected to be developed in the past two years.

Suburbs with significant areas beyond the reach of public transport include Deer Park, Caroline Springs and Burnside Heights.

BusVic executive director Chris Lowe said there was a lag between land developments being commissioned and the beginning of public transport services.

"If urban and transport planning were more integrated we may not have this lag," he said.

"A key objective of any new transport plan should be to ensure access to public transport services is available when residents are moving in and that the access is within 400 metres of their homes. If we don't plug this gap then we are just increasing Melbourne's dependency on private transport."

He called on the state government to make funds available to redress the growing backlog.

"There is also an element of inequity in terms of the scope of services on offer to those in the inner suburbs far exceeding the scope of services available to those living in the urban fringe," Mr Lowe said.

Long-time Caroline Springs resident Joy Cox said she was disappointed there weren't more bus services operating at local shopping centres.

"There are so many more people coming in and a lot of them wait around for long periods of time for buses to come," she said.

Transport Minister Terry Mulder's spokeswoman, Larissa Garvin, said BusVic's comments ignored a massive expansion of heavy rail to growth areas which would start from next year, including expansion of electrified train services to Sunbury.

"These rail extensions will provide a huge boost in public transport access for growth areas in the north and north-west," she said.

"The Regional Rail Link Project will provide a further expansion of heavy rail to our fastest growing areas in Melbourne's west, and the government has already started a study into a new rail line to Rowville in Melbourne's south-east."