Western Australian MP Melissa Price will be promoted to the environment portfolio as part of Prime Minister Scott Morrison's Cabinet shake up.

Ms Price, who represents the North West seat of Durack – the largest single member electorate in the world, assisted former environment minister Josh Frydenberg in the role and is understood to have supported Mr Morrison for the Liberal party leadership.

Melissa Price, MP for the world's biggest electorate, is set to become Australia's new environment minister. Credit:Alex Ellinghausen

She will take Mr Frydenberg's place in Cabinet after he was promoted to Treasurer following a brutal week in Canberra.

Ms Price was elected to represent the 1.6 million square kilometre seat in 2013 when she defeated former Kimberley Labor MP Carol Martin to replace Liberal Barry Haase.