Some members of the Senate are appointed by the government to assist ministers in their work. They are now referred to as parliamentary secretaries. In the past, persons who performed similar functions have been known by a variety of designations, including parliamentary under-secretary and assistant minister.
Parliamentary secretaries are now appointed under an amendment made in 2000 to the Ministers of State Act 1952, which prescribes the number of ministers under section 65 of the Constitution. The statutory provision provides for them to be appointed as ministers, but without that title or status. The purpose of this paradoxical provision is to allow them to be paid salary for the office without incurring disqualification under section 44(iv.) of the Constitution, which prevents members of either House holding an office of profit under the Crown, excepting only ministers.
Before the 2000 provision, parliamentary secretaries were appointed under the Parliamentary Secretaries Act 1980, and were not paid any remuneration of office but were reimbursed for expenses.
Since 1990, when the practice of appointing parliamentary secretaries was resumed, at least one senator has always been included in their number.
The first assistant minister to be appointed in the Senate was Senator E J Russell, who held that office during 1914-16. As assistant minister, Senator Russell answered questions (without notice and upon notice), laid papers on the table, initiated and controlled the passage through the Senate of legislation, moved other motions, and generally did all those things which a minister representing another minister in the other House does in the Senate. No special resolution or changes in the standing orders were made to enable Senator Russell to discharge the functions of a minister.
The legal status of parliamentary secretaries and the extent of their powers was the subject of debate on a number of occasions in the past; for further details see the report of the Senate's Standing Committee on Constitutional and Legal Affairs on The Constitutional Qualifications of Members of Parliament.
A continuing order of the Senate authorises parliamentary secretaries to exercise the powers and perform the functions conferred upon ministers by the procedures of the Senate, but they may not be asked or answer questions which may be put to ministers under standing order 72(1), or represent a Senate minister in respect of that minister's responsibilities before a committee examining the estimates.
The history of this order is as follows. The Parliamentary Secretaries Act 1980 did not define the powers or duties of a parliamentary secretary and thus did not settle the question of the extent to which senators appointed to such offices could exercise the powers and functions conferred upon ministers by the procedures of the Senate. In a statement to the Senate on this matter in June 1991, President Sibraa gave consideration to the question of whether secretaries could answer questions without notice on behalf of ministers and whether they could represent ministers at estimates committees. On 3 September 1991 the Senate adopted the following sessional order:
That any Senator appointed a parliamentary secretary under the Parliamentary Secretaries Act 1980 may exercise the powers and perform the functions conferred upon ministers by the procedures of the Senate, but may not be asked or answer questions which may be put to ministers under standing order 72(1).
During his term as Parliamentary Secretary to the Treasurer, 4 April 1990 to 24 March 1993, Senator McMullan appeared before estimates committees in place of the Treasurer and the Minister for Finance. On 6 May 1993 the Senate adopted a sessional order which contained, in addition to the provisions included in the order quoted above, a prohibition on parliamentary secretaries representing ministers before committees considering estimates.  The order was made permanent on 11 November 1998. This prohibition was subsequently relaxed to allow parliamentary secretaries to represent ministers other than Senate ministers in relation to the latter's own responsibilities.