A PARLIAMENTARY inquiry into planning decisions in Newcastle is set to issue an interim report recommending that the Boxing Day truncation of the city’s rail line be put off because of a flawed case for the project, including the lack of a cost benefit analysis.

If the government does proceed, then it must release advice to substantiate its assurances it doesn’t need an Act of Parliament to remove the heavy rail, and it must ensure light rail is installed immediately and runs down the existing rail corridor, the inquiry, chaired by Christian Democrats MP Reverend Fred Nile, is understood to have concluded.

The report will be issued on Thursday morning after being tabled to State Parliament, setting out over more than 100 pages the parliamentary committee’s interim findings in relation to the government’s transport changes, in order to get in ahead of the looming December 26 start of works.

A complete report, including findings about controversial changes to the city’s planning controls, is due by March 5.

It is expected the two government MPs on the committee, which is otherwise dominated by members opposed to the rail’s truncation, will dissent from the findings amid criticisms the conduct of the inquiry was politically motivated.

Mr Nile wrote on Tuesday to Premier Mike Baird, seeking a copy of any legal advice to support the government’s claims that an Act of Parliament is not needed for the rail works to proceed.

The Newcastle Herald has been told the report acknowledges no direct evidence has been found between allegations and evidence aired at the Independent Commission Against Corruption’s Operation Spicer and the government’s decision to cut the rail.

Mr Nile said on Tuesday ‘‘no clear links’’ had been established between the two, but whether proper processes had been followed came under heavy scrutiny in the report and the final report would look at such issues in  detail in relation to city planning controls.

As the Newcastle Herald has reported, the government says it does not believe it needs an Act of Parliament ‘‘at this stage’’ to remove the heavy rail infrastructure, depending on final plans for the soon-to-be vacant rail corridor land.

The committee had sought the advice from the Crown Solicitor, but was referred to the Premier’s office.

The Transport Administration Act states the government needs Parliament’s authority to close a rail line.

"A railway line is closed if the land concerned is sold or otherwise disposed of or the railway tracks and other works concerned are removed," the act says.

Save Our Rail president Joan Dawson wrote to Transport minister Gladys Berejiklian last week raising the issue.

The group is seeking advice as to whether a legal challenge can be mounted given the government doesn’t have Parliament’s endorsement, although a meeting scheduled for Monday with a lawyer was cancelled due to office evacuations associated with the siege in Sydney.

Newcastle Lord Mayor Nuatali Nelmes said seeking such advice was not a matter for the council, given the rail corridor was state infrastructure. ‘‘So they need to deal with that and the community expectations that they would follow the law,’’ Cr Nelmes said.