Perth: The Liberal Party is preparing for a landslide election loss in Western Australia on Saturday, a result set to spark calls for Prime Minister Malcolm Turnbull to put more distance between the federal party and Pauline Hanson's One Nation.

WA Liberal sources said the latest internal polling showed Premier Colin Barnett's approval ratings had collapsed in recent days and the party was set to lose between 13 and 20 seats.



Labor, led by Mark McGowan, needs an extra 10 seats to win government.

A controversial preference swap arrangement between the WA Liberal Party and One Nation – which Mr Barnett on Friday said he was uncomfortable with – has dominated the election campaign since it was announced. The deal saw the Liberal Party preference One Nation over alliance partner the Nationals in the state's upper house.



The outcome of the deal is seen as a test case for how the Coalition should respond to the One Nation threat in other states and federally.



Federally, attention will focus on Finance Minister and WA powerbroker Mathias Cormann who was involved in negotiations and has publicly defended the deal.

"There was already a lot of ill-feeling towards the government and the One Nation deal sealed that," a senior Liberal told Fairfax Media.