M25d constitutes the most South-West room of the office suite for the Leader of the Government in the Senate. Photographic evidence suggests the room would have operated as the main office in the suite, where day to day work would have been seen to and private meetings conducted. Today, the room displays two octagonal wooden library reading tables as part of a heritage furniture display.

The suite is one of four designed for key office holders in Provisional Parliament House. Others include offices for the Prime Minister, the Speaker, and the President of the Senate; these four suites are designed with respect to each other according to an axial grid.

The Leader of the Government in the Senate is a senior member of a government’s leadership team, but may lead a minority of senators if other parties dominate the Senate. The Senate Leader’s Suite features Blackwood wall panelling, decorative plaster air vents and clock with division bells. The Greek pattern leadlight glazing which survives in the built-in timber panelled cupboards and bookshelves is also of interest. All the furniture that occupies the room was made of Australian timbers, comprising blackwood, silky oak, Queensland maple, and cedar. Like much of the early surviving interiors of Provisional Parliament House, the Leader of the Government in the Senate’s suite reflects the refined simplicity associated with John Smith Murdoch’s Inter War Stripped Classical style.