Rogue Liberal MP Matthew Mason-Cox has forced his government into releasing the business case for the relocation of the Powerhouse Museum, in a move that could see him suspended from the party room.

In what has been described as an unprecedented step, Mr Mason-Cox crossed the floor of parliament to support a Greens' motion to have the business case released within 14 days.

The parliamentary order comes less than a fortnight after the government committed to releasing only a summary of the business case, and not until 90 days after its investment decision had been made.

Liberal MP Matthew Mason-Cox. Credit:Samuel Groves

A senior Liberal source said the upper house MP's decision to cross the floor could see a push to have him suspended from the Liberal party room.