One Nation wins first WA lower house seat in Secret Harbour by-election

One Nation has scored a historic win in Western Australia, securing its first lower house seat in the state.

The ABC's chief elections and data analyst Casey Briggs called the outer suburban seat of Secret Harbour for One Nation's Luke Herdegen a little over four hours after votes began to be counted.

One Nation's WA leader Rod Caddies claimed victory at 9.30pm local time, although Labor had yet to concede.

Labor's candidate was political staffer-turned-Woodside lobbyist Georgia Tree.

The area was traditionally safe Labor territory, having been held in different shapes and under different names since 1989, including most recently by Paul Papalia on an 11.5 per cent margin.

'Fight for our lives'

WA Labor Premier Roger Cook had repeatedly described the by-election as a "fight for our lives", given the threat posed by One Nation.

That the minor party was able to achieve such a large swing in Labor heartland will be watched closely around the country, both as an indication of the support behind One Nation and to learn lessons in how it can be campaigned against.

Mr Herdegen said his victory sent a loud message.

"There are no safe Labor seats in this state or in this country anymore," he said.

"The people have spoken today.

"None of these MPs are safe from the orange tsunami."

Mr Caddies said Australia's two-party political system was "dead".

"You're witnessing a result they said was impossible," he said.

"Labor owned this part of Perth.

"The working families out here would always vote Labor.

The area is home to a mix of older West Australians and young families, with new housing developments dotted along the coast, and shares many similarities with areas in other states where One Nation has performed well in recent elections.

Mr Herdegen is a gym owner who said he moved to Western Australia three years ago because there were better business opportunities.

He campaigned on a wide array of issues including how often red bins were being collected in the area, local housing pressures and migration.

After being pre-selected, an old social media post emerged in which he spoke about heavy cocaine use and being connected to the Albanian mafia while living in London a decade ago.

"That's a story I put out there to try and help inspire people to live happier and healthier lives and I think it really did help a lot of people," Mr Herdegen said at the time.

Speaking on News24, formerly known as Sky News, One Nation leader Pauline Hanson said people were turning to her party for hope.

"They're wanting someone who's really going to listen to them and really go out and fight for them to change the direction this country is going in," she said.

"And I give them my solemn oath I'm trying to get the right people on the floor of parliament to do that for the Australian people, to give them back our country that's been stripped away from us every which way."

Speaking before the result was known, WA Premier Roger Cook said Ms Tree had "delivered a hell of a fight".

"This campaign has been a reminder that Western Australians are doing it tough," he said.

"People are concerned about their lifestyle and their futures."

Mr Cook urged the party faithful to use the disappointment of the result to work harder.

"Seize those emotions and build on them, let it galvanise us for the fight of the future."

Voters wanted change

Many voters the ABC spoke to before the election highlighted a desire for change and a frustration with local, state and federal governments.

Labor will be able to take some heart from the fact that by-elections can often produce results which differ from general elections, because the government of the day won't change no matter the outcome.

But the result remains a significant blow for the party which has been dominant in WA for nearly a decade.

Leader of the WA opposition Basil Zempilas had claimed a win for One Nation would be a win for his Liberal party, because it would show falling support for Labor.

It prompted a fierce rebuke from federal MP Andrew Hastie who accused Mr Zempilas of accepting defeat.

His seat of Canning overlaps with Secret Harbour and is expected to be targeted by One Nation at the next federal election, making any lessons from this by-election particularly pertinent for him.