CALDERWOOD, on 700 hectares of dairy farms under the Illawarra escarpment, is one of the least suitable places for a town in the Illawarra, the NSW government regional planning strategy states.

But in January, the then planning minister, Tony Kelly, gave Delfin Lend Lease approval to develop 4800 houses and 50 hectares of shops and industry.

Now, Shellharbour City council is suing the government over that decision. The council argues the site comprises prime agricultural land that should be protected from development and that it sits on a floodplain, making development risky.

Opponents say the approval for Calderwood upends the government's own plan for land release in the region, which identified West Dapto as the next greenfield site for release. Only after West Dapto's development was Calderwood to be opened up.

The council administrator David Jesson, a Labor appointee, has not made public the grounds of the legal challenge: ''We've got some concerns over the process that has been followed … we're not altogether happy that it was as it should have been.''

The new Liberal MP for Kiama, Gareth Ward, said the planning process had been ''usurped''.

Toni Milis, the head of Delfin Lend Lease, said: ''Calderwood is a significant project …and the project was approved under a merit based assessment process.''

A Department of Planning spokeswoman declined to comment as it had not yet been served with council's points of claim.

Kelsey Munro