CANBERRA, Australia - A former senior government minister gave a tearful farewell speech to Parliament on Wednesday, warning that Australia's ability to implement policy had been undermined by "the revolving door in Australian politics."

Joe Hockey announced he was quitting Parliament after Prime Minister Tony Abbott was replaced by Malcolm Turnbull last month in a shock leadership vote of lawmakers in the ruling conservative Liberal Party. Hockey had been treasurer, which is regarded as the government's most important portfolio after the prime minister.

Australia has had five prime ministers in five years and four treasurers in four years during an extraordinary period of political volatility.

Hockey told Parliament the stability of Prime Minister John Howard's conservative government, which was voted out in 20007 after more than 11 years in power, "has been replaced with rapid and unpredictable changes of government."

"Most public servants are very good, but some - confused by the inconsistency of policy and the rapid change in the number of ministers - they will simply wait out a minister or a government when they are asked to implement very difficult decisions," he said.

While many commentators agree the political instability threatens policymaking, opinion polls show the shift to Turnbull has been popular with the public.

Howard was Australia's second-longest serving prime minister. He was ousted by Kevin Rudd, whose centre-left Labor Party replaced him with his deputy, Julia Gillard, ahead of elections in 2010. Rudd then ousted Gillard ahead of 2013 elections, which Abbott won with a promise of stable government.

Hockey, who spent 19 years in Parliament, is tipped to become Australia's next ambassador to the United States.

Abbott remains a member of Parliament, but was overseas Wednesday. Abbott has said he will decide his future around Christmas.