Colin Barnett

Barnett in 2012

On 4 August 2008, Troy Buswell resigned as Opposition Leader and two days later Barnett was re-elected unopposed to the Liberal leadership despite the fact that he had previously announced his retirement and Deidre Willmott (who would subsequently be appointed as his Chief of Staff)[15] had been endorsed in his electorate. On 7 August 2008, Premier Alan Carpenter called an early election for 6 September 2008. Barnett led the Liberal Party to the election, which saw a significant swing away from the incumbent Labor Party, leading to a hung parliament. The balance of power rested with the WA Nationals. While the federal Liberals and Nationals are in Coalition at the federal level, the WA Nationals do not necessarily follow their federal counterparts' lead politically. Knowing that Nationals leader Brendon Grylls was in a position to effectively choose the next premier, both Barnett and Carpenter courted the Nationals' support.

A week after the election, the Nationals agreed to support the Liberal Party as a minority government. As part of the deal, Grylls and two other Nationals accepted posts in Barnett's cabinet. However, the National ministers had only limited cabinet collective responsibility, unlike past Liberal-National coalitions in Western Australia (and at most levels in the rest of the country), and the Nationals reserved the right to vote against the government on issues that affected their electorates' interests. Additionally, Grylls was not appointed Deputy Premier, a post which went to Liberal deputy leader Dr Kim Hames.[16] Carpenter resigned rather than face certain defeat on the floor of the Assembly, and Barnett was sworn into office on 23 September 2008.

Barnett was the sole state premier opposed to Labor Prime Minister Kevin Rudd's key Health reform policy deal at the April 2010 COAG meeting. Barnett at the time led the only Liberal State Government in Australia, while all others states were led by Labor Governments. The reasoning for Barnett's strong opposition towards the reform was because it would require the State Governments to forfeit a proportion of their GST revenue. The Rudd Government's proposal was that 30 per cent of the GST revenue pool was to be dedicated towards the Commonwealth's contribution for hospital services, which had a disproportionate impact on those States receiving a less than per capita share of the GST pool (for Western Australia, this would have resulted in an estimated 64 per cent of GST revenue being forfeit). Barnett had already been angered that Western Australia was given a decreased 7.1 percent amount of the GST revenue (lower than last year's revenue amount of 8.1 percent)[17] while Western Australia is a state that will be heavily relied upon for the nation's economic growth due to its booming resource sector. Western Australia therefore would be heavily dependent on GST revenue to fund major resource sector projects although they would not be supported by GST revenue, thus becoming extensive expenditure for the state.[18]

Barnett believed that if Western Australia had agreed to a proposition for the States to handover 30% of the GST revenue pool, the arrangement could eventually lead to the federal government being able to acquire 100% of the state's GST revenue. The reaction of Barnett towards the health reform has been considered by political writer Peter van Onselen as a preservation of the states' rights.[19]

From 27 April 2010, Barnett held the Treasury Portfolio after the resignation of former Treasurer Troy Buswell. In a cabinet reshuffle he handed the portfolio to Christian Porter later that same year.[20] Barnett returned to the treasury portfolio when Christian Porter suddenly decided to pursue a career in federal politics and resigned immediately from all his state ministerial portfolios on 12 June 2012. Porter's resignation saw Barnett serve as an interim Treasurer until he was officially replaced by Troy Buswell the following month on 7 July.[21]

Barnett led the Liberals to victory in the 2013 state election, taking 31 seats on a swing of 8.8 points. This was theoretically enough for the Liberals to govern alone, and marked only the second time that the main non-Labor party in Western Australia had won a majority in its own right since adopting the Liberal banner in 1944. However, Barnett said after the election that the coalition with the WA Nationals would be retained.[22] According to ABC election analyst Antony Green, Barnett would have been forced to keep the Nationals in his cabinet in any event. Even after the 2008 electoral reforms, rural areas are still significantly overrepresented in the Legislative Council. Green argued that the rural weighting in the Legislative Council makes it politically impossible for a Liberal premier to govern without National support, even when the Liberals win enough Legislative Assembly seats to theoretically govern alone.[23]

In October 2004, Barnett led a campaign to raise the age of consent for homosexual acts from 16 to 18. This policy of recriminalisation was opposed by several major organisations, including Amnesty International, the World Health Organization, and the Australian Medical Association, as well as all other parliamentary parties, including the Nationals.[24]

In October 2009, Barnett announced a series of new policies relating to drug legislation including a repeal of the Cannabis Control Act 2003.[25] The previous laws were formulated by Geoff Gallop's drug summit, taking input from experts such as academics, police, social workers, lawyers, medical professionals and members of the public.[26] Barnett has stated it is his intention to overturn these laws because of his beliefs and stated that the drug summit members made a mistake introducing them[27] and that cannabis was a "gateway drug".[28] To help with the enforcement of this new policy, Barnett also supported legislation to give police the power to search and seize property without any suspicion or belief that a crime has been committed.[29] A Liberal parliamentarian, Peter Abetz, voiced support for these laws in parliament by drawing reference to the work Adolf Hitler did to bring security to Nazi Germany.[30][31] Barnett said that Abetz was making a valid point.[32]

In June 2013, Barnett said that Western Australia would not sign up to the Gillard Government Gonski School Funding Reforms. Barnett said that he will not let the federal government govern schools.[33]

In December 2013, Barnett announced a controversial plan for great white sharks to be shot and disposed of at sea if they come within one kilometre of the coast of Western Australia, while acknowledging broad dissent in the community.[34][35][36]

In 2015, former Liberal leader Bill Hassell—who had preceded Barnett as the member for Cottesloe and "has a habit of excoriating Barnett in the media" according to The Australian—labelled Barnett a social liberal and a useful over-spender. Barnett claimed mining royalties were spent on "disability, mental health and other areas of social need". In December 2007 when former Liberal leader Barnett was once again a backbencher and contemplating political retirement, he claimed: "I'm disappointed that the Liberal Party has been taken over by hardline right-wingers" and "The party has become inflexible and has held a hard line on social issues, and that has not worked with 30-year-old voters" and "We should be more moderate on social issues. Saying sorry to Aboriginal people is part of that. We should have said sorry long ago".[37]

On 17 September 2016, Local Government Minister Tony Simpson and Transport Minister Dean Nalder resigned from Cabinet.[38] Subsequently, a motion to spill the leadership of the WA Liberal Party was brought by backbencher Murray Cowper. On 20 September, it was defeated 31 votes to 15. Nalder, who would have nominated against Barnett if the spill motion had passed, promised not to launch future leadership challenges.[39]

Most polls since Barnett's landslide victory in 2013 showed the Barnett government well behind Labor. A Newspoll conducted from October to December 2015 and released in January 2016, revealing the government significantly trailing 47–53 two-party against the Labor opposition, representing a double-digit two-party swing of more than 10 points since the 2013 election. Had this been repeated at an election, it would have been more than enough to deny Barnett a third term. Just prior to the 2013 election, Barnett was nominated Better Premier with a 21-point lead on 52 percent, with an approval rating of 51 percent and a disapproval rating of 36 percent. Since then, Labor leader Mark McGowan has consistently led Barnett as Better Premier by several percent, with Barnett's approval rating consistently low, currently at 33 percent, with his disapproval rating consistently high, currently at 54 percent.[40][41][42][43]

On 11 March 2017, Barnett was swept from power in the largest defeat of a sitting government in Western Australia's history. The Coalition suffered a swing of 12.6 percent and lost 20 seats. Seven members of Barnett's cabinet, including Grylls, were defeated. The Coalition took a particularly severe beating in Perth. It went into the election holding 26 of the capital's 43 seats, but many Liberals in the outer suburbs sat on inflated margins. The Liberals suffered a 13.6 percent swing in Perth, and were cut down to just nine seats there, including Barnett's.[44][45][46][47][48] Barnett resigned as Liberal leader and returned to the backbench; he was succeeded as WA Liberal leader by his former Treasurer, Mike Nahan.

On 15 December 2017, Barnett announced his intention to retire from politics after Australia Day 2018. He resigned on 5 February 2018, triggering a by-election in his seat of Cottesloe.[49]

In December 2019, Barnett criticised Home Affairs Minister Peter Dutton for stating that the values of the Communist Party of China are "inconsistent" with Australian values.[50]