Western Australia's depleted Nationals and Liberals have formed an opposition alliance after Labor won control of both houses of parliament.
Mia Davies will serve as opposition leader after her Nationals party outpolled the Liberals in the lower house at last month's state election.
The decimated Liberals have been reduced to just two lower house MPs with Labor claiming 53 out of 59 seats.
WA's Nationals-Liberals partnership will not be a formal coalition, allowing the parties to disagree on some policy positions.
But Ms Davies said both parties were committed to "restoring the integrity" of the Royalties for Regions fund which had previously been criticised by the Liberals.
"We both agree that Royalties for Regions needs to be restored and rejuvenated after four years of misuse and manipulation by the Labor government," Ms Davies said.
"As the leader of the Nationals and the opposition, you can expect our team to continue to argue strongly for investment and support for regional communities across this state."
The deal includes a sharing of resources and a splitting of portfolios, with Nationals MP Shane Love to serve as deputy opposition leader.
Newly-appointed Liberal leader David Honey will serve in the state development and energy portfolios and his deputy Libby Mettam is responsible for health.
Dr Honey said the alliance would hold the McGowan government to account and ensure it does not "become arrogant because of its huge parliamentary majority".
"I am very confident that this positive co-operation between the Liberals and Nationals WA will grow even stronger over the next four years and make our combined efforts highly effective in the lead up to the 2025 state election," he said.
The parties had previously worked together in government and opposition but were not aligned in the first term of the McGowan government.
Parliament will commence on April 29 with 13 new lower house Labor MPs to be sworn in at a joint sitting opened by Governor Kim Beazley.
Micro party candidates, including two from Legalise Cannabis WA, managed to claim three upper house seats.
Daylight Saving Party candidate Wilson Tucker was elected in the Mining and Pastoral region despite polling just 98 votes.