Today there are 76 senators – 12 from each of the 6 states and 2 each from the Northern Territory (NT) and the Australian Capital Territory (ACT). This has been the total number since 1983 when it increased from 64.
The number of senators is largely determined by the Australian Constitution and, although the number can be increased (or decreased) by the Australian Parliament, there are restrictions on making any changes.
Section 7 of the Australian Constitution guarantees equal representation between the original states of the Commonwealth of Australia. This section also tells us that ‘no Original State shall have less than six senators.’ Hence, the first Senate met with 36 senators (6 senators from 6 states) and, unless an original state stopped being part of Australia, this would be the minimum number of senators.
Section 122 permits the Australian Parliament to decide how many, if any, senators a territory may have in the Senate. The Senate (Representation of Territories) Act 1973 allowed the ACT and NT to elect 2 senators each at future federal elections. This number continues today but could be changed by another act of Parliament.
A further consideration is Section 24, sometimes known as the ‘nexus provision’. This section requires that the number of members of the House of Representatives must be twice the number of state senators, or as near as possible. This means that any change to the number of senators will have a significant impact on the House of Representatives. For example, in 1948, Parliament increased the number of senators from 36 to 60 (10 each from the 6 states) and the members of the House of Representatives increased from 75 to 123.