The Berejiklian government has evaded a parliamentary order requiring it to produce the business case that justifies the relocation of the Powerhouse Museum to Parramatta.

Coalition backbencher Matthew Mason-Cox risked suspension from the Liberal Party room to cross the floor of the Upper House in support of a Greens' motion to have the critical set of documents released within 14 days.

The Powerhouse Museum in Ultimo. Credit:Louise Kennerley

At the close of business on Thursday night, the secretary of the Premier and Cabinet, Tim Reardon, asserted to the Parliament that no documents covered by the resolution were held by the Office of the Premier, the Office of the Minister for Arts, Department of Planning and Environment, including Create NSW, and Infrastructure NSW.

This seems at odds with Arts Minister Don Harwin's own statement to the Herald earlier this month in which, through a spokesman, he said: "The business case was delivered to the government in December, and has since been going through a number of assurance processes that need to be completed before an informed decision can be made."