One Nation declares there are 'no safe Labor seats' after historic by-election win

One Nation has declared victory in the battle for its first Western Australian lower-house seat, with nearly 75 per cent of votes counted in a state by-election.

Pauline Hanson's party claimed the Secret Harbour by-election late on Saturday evening AEST, however Labor candidate Georgia Tree is yet to concede.

One Nation's Luke Herdegen held a 14.08 per cent lead over Tree in the two-candidate preferred vote, when WA Electoral Commission counting closed on Saturday with 74.54 per cent of the vote counted.

"There are no safe Labor seats in this state, or in this country any more," Herdegen told a jubilant crowd.

Herdegen secured 39.08 per cent of first-preference votes, according to the electoral commission, ahead of Tree's 24.43 per cent and Liberal candidate Ryan Robertson's 17.29 per cent.

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WA One Nation Leader Rod Caddies noted the historic moment as he declared "the two-party system is dead".

"Labor have owned this part of Perth. But a safe seat does not stay safe if you ignore it long enough.

Herdegen has been buoyed by a sea of polling booth orange across the beach-side electorate, south of Perth.

"The vibe has been really strong for the last six weeks," he told AAP earlier on Saturday.

"We're feeling confident but ... it's a big margin. The swing is definitely on but it's just a matter of how big."

One Nation's performance in WA will be of interest across the nation, particularly Victoria with a state election looming in November.

On the ground in Secret Harbour, Labor is on the nose, with cost-of-living pressures, housing and a perceived lack of community amenities topping lists of voter concerns.

Local Luke Pors voted for One Nation and believes it will do a better job than either Labor or Liberal.