These files were created in the Prime Minister's Department following the separation of Prime Minister's Department and the Cabinet Office in March 1968. As the Prime Minister's Department retained the function of advising the Prime Minister on Cabinet business, the Prime Minister's Department was supplied by the Department of the Cabinet Office with copies of all current Cabinet documents and, where requested, with photocopies of documents of earlier Liberal Governments commencing in December 1949.

The two departments were amalgamated in March 1971 into the Department of Prime Minister and Cabinet but the files were maintained until early 1972 as the two segments of the new department were physically separated. 

Following the accommodation of the Department in one building these files were closed and handed over to the custody of the Cabinet Office.

The files have yellow covers and contain submissions, decisions and briefing notes. The system of arrangement and control is similar to arrangements in force in the Cabinet Office. Files C99 and C498 are missing.