Dr Malcolm Arthur Colston (5 April 1938 – 23 August 2003), Australian politician, was a Senator in the Parliament of Australia representing the state of Queensland between 1975 and 1999. He was a member of the Australian Labor Party (ALP) until 20 August 1996, but then resigned from the party and sat as an independent until his retirement from the Senate.
Colston indirectly played a role in the 1975 Australian constitutional crisis.
On 30 June 1975, Queensland ALP Senator Bertie Milliner died suddenly. The Labor Party nominated Colston to fill the casual vacancy in the Senate. The Constitution provides that a Senate casual vacancy is filled by a person chosen by the relevant state parliament. Although it did not become a constitutional requirement until 1977, it had been longstanding convention that the state parliament choose a person nominated by the departing Senator's party. However, the Premier of Queensland, Joh Bjelke-Petersen, claimed that Colston was a "dangerous socialist" and refused to appoint him. Officially though, Bjelke-Petersen expressed doubts over Colston's integrity and instead appointed Albert Field, who was a member of the Labor Party but was staunchly opposed to the policies of the Gough Whitlam Labor government.
The ALP challenged Field's appointment in the High Court, and he was on leave from the Senate almost from the day of his appointment. This gave the Coalition a greater advantage, and it was therefore a crucial event in the events leading up to the dismissal of the Whitlam government.
At the ensuing 1975 election, Colston was elected as a Labor senator. He continued to serve in that capacity until 1996.
After the 1996 election, the Labor Party refused to nominate him to become Deputy President of the Senate. In a bid to win him over, the Howard Coalition government offered to support him. He resigned from the Labor Party by fax message at 11:30 am on 20 August, and he took his seat as an independent that afternoon. In the evening he was elected Deputy President, on the nomination of the Coalition. While he opposed the Coalition's industrial relations package, he voted for the sale of a third of Telstra and some other government initiatives. Colston subsequently sat as a "Queensland First" senator.
In 1997, Colston was charged by the Commonwealth Director of Public Prosecutions with 28 charges of defrauding the Commonwealth by allegedly misusing his parliamentary travel allowance. He then revealed that he was suffering from cancer. Prosecution was not pursued after medical opinion was provided that Colston was unlikely to live long enough for a trial to be completed. In the event, he survived for a further six years. He retired from the Senate at the end of his term on 30 June 1999.
Mal Colston died in 2003.