The McGowan government on Tuesday used its control of the parliament to secure the passage of its electoral equality legislation.

From the next election in 2025, WA's six Legislative Council districts will be abolished.

Upper house MPs will instead be elected by the entire state, with regional votes no longer carrying greater weight than city votes.

The change has been criticised by the WA Nationals, who claim it will disenfranchise regional voters by reducing their representation.

"This is a dark day for regional WA - their voices have been silenced, they have been refused a seat at the decision-making table, and their representation has been killed off," Opposition Leader Mia Davies said on Wednesday.

Labor already holds 53 out of 59 lower house seats and an unprecedented upper house majority after a landslide election win in March.

Premier Mark McGowan sought electoral changes soon after the victory, despite having assured voters during the campaign that such a move was not on his agenda.

An expert committee led by former governor Malcolm McCusker was tasked with examining the system, and in particular malapportionment in regional areas. The committee endorsed changes to the system in a report in September.

Each upper house region currently elects six representatives regardless of their populations.

The government has said votes cast by people in the Mining and Pastoral region at the last election were worth 6.22 times more than those cast in the metropolitan area.

Ending malapportionment could reshape the upper house given the Nationals' traditional dominance in regional areas.

The premier declared it a historic moment for the state.

"All Western Australians want, and indeed deserve, a fair voting system - and we are delivering just that," he said in a statement.

"One person's vote should not be worth more than another's just because they live in a different part of the state."

Under the changes, voters will elect 37 upper house MPs rather than the current 36.

WA will also abolish group voting tickets, which allow parties to dictate the preference distribution when electors vote above the line.

The tickets have been manipulated through "preference harvesting" to get minor parties elected, including at this year's election.

Daylight Saving Party candidate Wilson Tucker was elected in the Mining and Pastoral region with 98 votes - a figure believed to be the lowest primary vote for a candidate elected to any Australian parliament.

His victory was made possible by preference deals which also catapulted Legalise Cannabis WA candidates to victories at the expense of the Greens.

The opposition said the priority legislation had been forced through without sufficient consultation.

"Labor did not give West Australians the chance to have their say on this before or after the election - they've just used their massive numbers to do what they like," Ms Davies said.

Australian Associated Press