A fast train network connecting greater Sydney, Wollongong and Newcastle as a "mega region" could create more than 10,000 new jobs, according to a new report.

A planning lobby group, the Committee for Sydney, said such a rail network could slash the commutes from Gosford to Sydney, and from Wollongong to Liverpool, by half.

The report said even a moderately fast rail network, which reaches speeds of 200 kilometres per hour, could connect Newcastle, the Central Coast and Wollongong with western Sydney in less than one hour.

Connection Current speed New speed Newcastle to Gosford 66 minutes 35 minutes Gosford to Sydney 80 minutes 40 minutes Newcastle direct to Parramatta (missing the Central Coast) 153 minutes 60 minutes Wollongong to Sydney CBD 85 minutes 60 minutes Wollongong to Liverpool via Campbelltown 124 minutes 60 minutes

Housing affordability to improve

Building new housing along such rail corridors could take the pressure off the Sydney housing market, the report said.

The Committee for Sydney has spent a year investigating the potential of improving links between Sydney, the Central Coast, Newcastle and Wollongong in what it is describing as a "mega-region".

It estimates that if an extra 40,000 homes were built along the new rail corridors, that could deliver more than $75 billion of housing affordability improvements.

It also said such a rail network could create 4,725 new jobs for Wollongong, 3,875 for Gosford and 3,225 for Newcastle.

The Committee is calling this interconnected area "the Sandstone mega-region".

It is following the lead of mega-regions in the Netherlands and south-east China, which it said has delivered improved economic and social outcomes for their communities.

The Committee said the area covered by the mega-region is already home to more than 70 per cent of the state's population and nearly 25 per cent of the national population.