Premier Mike Baird has dismissed claims the government's controversial plan to truncate the Newcastle rail line falls outside of the law.

Opposition Leader John Robertson has written to Mr Baird demanding he release any legal advice his government is relying on to remove the rail line.

Mr Robertson says under NSW law, a rail infrastructure owner must not close a railway line unless authorised by an act of parliament.

But Mr Baird has dismissed those claims as political "stunts".

The premier said the truncation, which is part of his government's measures to revitalise Newcastle, was long overdue.

"I say to the leader of the opposition, get out of the way. Just get out of the way," Mr Baird said.

"Enough's enough. Too much talk. (It's) time for action."

Mr Robertson earlier said the government had no legal basis to close to the rail line.

"Without a further act of parliament, any tampering or removal of any physical infrastructure associated with the operation of the rail line ... would be in breach of the law," he said in a statement.

The rail line plan is a major issue in the Newcastle region, where two Labor MPs have recently been elected to state parliament in ICAC-triggered by-elections.

© AAP 2014