Minister for the Environment and Heritage (2004–07)

In July 2004, a pre-election reshuffle saw Campbell become Minister for the Environment and Heritage. In this role, he acknowledged the need for action on climate change but argued that it was important to consider environmental issues in an economic context.^[3][4] Amid growing community concern over the issue, he also argued for a "post-Kyoto arrangement that is effective" and a "portfolio approach" to the issue, rejecting the notion of "silver bullet" solutions.^[5][6]

Campbell was a vigorous critic of whaling. Through the International Whaling Commission, he actively campaigned against commercial and "scientific" whaling.^{[7][8][9][10]}

In 2006, Campbell drew criticism for blocking a wind farm project in south-eastern Victoria on the basis that it may pose a risk to the critically endangered orange-bellied parrot. Commentators and the opposition rejected the decision as inconsistent and politically motivated.^[11][12][13]

In 2006, Campbell was criticised for the approval of the Cloud Break mine in the Pilbara region of Western Australia, because of the number of endangered species in the area of the future mine, among them the incredibly rare night parrot.^[14]

Minister for Human Services (2007)

In January 2007, a cabinet reshuffle saw Campbell appointed Minister for Human Services, which was elevated to a cabinet position. However, on 3 March 2007, Campbell resigned after revelations he had met disgraced former Western Australian Premier Brian Burke. The resignation came in the midst of Liberal Party attacks on Opposition leader Kevin Rudd for also having met with Mr Burke, and was seen as a strategy to pressure and undermine Rudd. Prime Minister John Howard defended Campbell from charges of any moral wrongdoing, despite deputy leader Peter Costello's claim in Parliament that anyone who dealt with Brian Burke was morally compromised.^[15][16]

Campbell announced his retirement from politics on 4 May 2007, saying that the Prime Minister had told him the door was still open for a return to the cabinet, but that he had decided to pursue a career in the private sector.^[17] The Liberal Party in Western Australia chose Mathias Cormann to take his place.^[18] Campbell formally resigned his Senate seat on 31 May 2007.