One Nation has claimed victory in the federal seat of Farrer, delivering an enormous byelection blow to the Coalition.

David Farley was leading the two candidate-preferred count over his nearest rival, independent Michelle Milthorpe, by about 60 per cent to 40 per cent at 8pm.

He danced on stage with leader Pauline Hanson, who said "this is not only a win for Farrer, it's a win for the rest of Australia".

"Millions are watching on their TVs now and I believe it's giving them hope ... to get our country back," she said.

After playing John Farnham's You're The Voice and a round of "Aussie Aussie Aussie, oi oi oi", Farley told supporters he was humbled.

"You listened, you agreed, and you spoke tonight. So thank you, Farrer," Farley said.

"We're like a mason with a chisel and hammer and we're recarving the letters into the Australian democracy.

"One Nation has reached the end of its beginning, we're going through the ceiling from here."

Hanson said she "got a tear in my eye" as the Farrer result was called for One Nation.

"Until it's called you have no idea that I've been sort of on eggshells ... until it's called you really don't understand the journey that I've been on," she said.

Votes were still being counted but projections indicated a massive victory for One Nation.

It is the first time a One Nation candidate has been directly elected to the House of Representatives, and the byelection is being widely considered a temperature check of voter dissatisfaction with the major parties, particularly Liberal voters in conservative heartland.

Catastrophic result for Liberal Party

Voters have abandoned the Liberal Party in huge numbers in the seat of its former leader Sussan Ley.

It is the first time in Farrer's 77-year history that it has not been held by the Liberal or National parties.

Liberal candidate Raissa Butkowski attracted only about 10 per cent of the vote, and leader Angus Taylor said the party "must change".

"This byelection was always going to be a mountain to climb for the Liberal Party," he said.

"For too long we have been a party of convenience, not of conviction, and that must change.

"Over the last year or so the Coalition hasn't done what it should do: been united and stable and strong, with two breakups of the Coalition over that time.

Butkowski said that while "we copped quite a kicking", there was still hope for the Liberals.

"I think that there is still a lot of goodwill for the Liberal Party in the regions, in Albury, across the country, but possibly people just wanted to try something different this time," she said.

"Angus has been very clear that he's committed to working hard to rebuild the trust, not only across Farrer but across the country."

Former Nationals leader Barnaby Joyce, who defected to One Nation, echoed his new leader's declaration that the Farrer win was "a result for Australia".

"Australia's changed, Australia's changed, Australia's changed ... there'll be a bomb going off in Canberra right now," he told the ABC.

He said he expected One Nation to win more seats across the country and criticised Taylor's "incredible speech from a guy who got 11 per cent" of the votes in the Farrer byelection.

"That's like hearing a victory speech from the person who came fifth in the heats," he said.

Ley, who vacated the seat when she resigned from parliament after the leadership spill won by Taylor, congratulated Farley and delivered a message to her successor.

"I urge the Liberal leadership to accept this result with humility because the voters never get it wrong," Ley said in a statement.

"On the day the leadership spilled in February, the new leader said the Liberal Party needed to 'change or die'.

"Three months later, the result in Farrer demonstrates that statement to be far truer today than it ever was."

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