Warburton was elected at the 1977 election as the Labor Party candidate for the seat of Sandgate, succeeding Harold Dean who had held the seat for the ALP since 1960. In 1982, following a string of poor election results under Ed Casey, a leadership contest lead to fellow opposition frontbencher Keith Wright defeating Casey in a secret ballot. Warburton was appointed deputy opposition leader in Wright's shadow cabinet, despite having served only five years in parliament. Warburton became a member of the then dominant Trades and Labour Council faction, an affiliation he retained during his later career.
In 1984, Wright resigned from the Legislative Assembly to stand for election to federal parliament. Warburton was elected by caucus as the new Labor leader in Queensland on 29 August 1984. Warburton was often portrayed in the media as being an "old style" Labor leader; uncomplicated and honest. Peter Bowers, a columnist with the Sydney Morning Herald declared that Warburton was "...a straight up and down politician, no charisma, no nonsense". Labor approached the 1986 election being given little hope of taking power, given the continued existence of the Bjelkemander, despite continued disunity and infighting between the Liberal and National parties that formed government. Warburton's policies included the introduction of random breath testing in Queensland, and a ban on uranium mining in Queensland, an idea that would become longstanding Labor party policy. Warburton also made overtures to the Liberals, offering to form a coalition government with them in order to break the National Party's grip on power. However, on polling day, the National party won a resounding victory that enabled them to govern in their own right, and Labor lost two seats, despite polling more votes than the Nationals. Warburton hung on as leader of the opposition after this defeat, but eventually handed over the party leadership to Wayne Goss in 1988.
In addition to his political career, Warburton was also an enthusiastic participant in the sport of lawn bowls.
Death
Warburton died on 5 August 2018 on the Sunshine Coast. At the time of his death he was the only surviving ALP leader who did not become Premier and the last surviving Opposition Leader who had led his party during its 32 years in Opposition between 1957 and 1989.