Federal Treasurer Josh Frydenberg and rookie Liberal MP Gladys Liu are facing a last-minute High Court challenge to their victories at this year's federal election.

Key points: High court challenges have been lodged against election results in Kooyong and Chisholm

High court challenges have been lodged against election results in Kooyong and Chisholm The seats were won by Liberal MPs Josh Frydenberg and Gladys Liu

The seats were won by Liberal MPs Josh Frydenberg and Gladys Liu The challenges centre on posters that appeared outside voting booths on election day

Failed independent candidate Oliver Yates, who challenged Mr Frydenberg in the seat of Kooyong, has teamed up with a mysterious voter from Ms Liu's seat of Chisholm to launch a legal bid to have the results in both electorates ruled invalid.

The challenges centre on Chinese-language Liberal Party posters that appeared at voting booths on election day, which they said were designed to deceive voters.

Documents filed to the High Court, sitting as the Court of Disputed Returns, claimed the posters imitated official Australian Electoral Commission (AEC) material and were therefore in breach of electoral laws that make misleading and deceptive conduct illegal.

'Misleading' posters officially authorised

The posters were authorised by the Liberal Party and used similar colours to the AEC. ( ABC News: Gemma Hall )

The posters, which featured the AEC's distinctive purple and white colouring and were written in Chinese, instructed voters at polling stations that the "correct way to vote" was to place a "1" next to the name of the Liberal candidate on the ballot paper.

They were officially authorised by the Liberal Party's Victorian state director in small text at the bottom of the poster.

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Mr Yates flagged on Friday that he would begin the legal action this week, but a challenge to Ms Liu's knife-edge victory in Chisholm appeared unlikely after Labor indicated it would not dispute the result in that seat.

But now Ms Liu has been swept into the proceedings after Mr Yate's legal team began representing a Chisholm voter named Leslie Hall.

Ms Liu is the first Chinese-Australian woman to gain a Lower House seat in Federal Parliament. ( ABC News: Marco Catalano )

Marque Lawyers principal Michael Bradley, who is acting in both matters, would not go into detail about how Ms Hall became involved in the proceedings.

"She is a private citizen, she is an elector in Chisholm and she made the decision that she was sufficiently unhappy about the conduct of the Liberal Party on election day," Mr Bradley told the ABC.

"Somebody — either a candidate or elector — has to stand up and be the petitioner and she's decided that she is prepared to do that. She has no political axe to grind and nothing to gain out of it."

Ms Hall's application also asks the court to make a declaration that Ms Liu, as well as acting Victorian Liberal Party director Simon Frost, committed illegal activity by authorising the posters.

In a statement provided by her lawyers, Ms Hall said she was concerned the posters represented an "erosion of democracy".

"I am concerned that the AEC allows deliberately misleading statements in a foreign language to be provided to people who may not have access to English and therefore to a full understanding of the electoral processes," she said.

Independent candidate Oliver Yates is challenging the result of the seat of Kooyong. ( Supplied: Oliver Yates )

Mr Yates' application asks the court for a declaration that Mr Frydenberg engaged in illegal activity.

Today marks the 40-day deadline for disputing the election result.

The Liberal Party has insisted the posters were not misleading and complied with all electoral rules.

"The signs were properly authorised as required by the Commonwealth Electoral Act," Mr Frost said in a statement.

"The Liberal Party will be vigorously defending our position."

Mr Frydenberg and Ms Liu have been contacted for comment.

In a statement today, Labor said it believed the signs had "the clear purpose of misleading Mandarin and Cantonese-speaking voters," but it would not launch a legal challenge to the outcome because of the cost and time involved in legal proceedings.

Mr Yates told the ABC he was making the challenge as he believed the current electoral rules allowed for voters to be misled.

"I wouldn't be doing it if I didn't think there was a very important point to be made here," he said.

"If people believe that engaging in misleading and deceptive conduct is something that should be condoned ... they are wrong."

Ultra-thin win in Chisholm

The AEC has previously ruled the posters were not in breach of the Electoral Act because they were properly authorised and the AEC "does not own the colour purple".

The challenges claim posters such as this were designed to "trick" people into voting for the Liberal Party. ( ABC News: Gemma Hall )

But the applications argued the posters were deceptive because they led voters to believe that "in order to cast a valid vote, the number '1' had to be placed on the green ballot paper that was next to the Liberal candidate".

Ms Hall's application said the posters were particularly effective in Chisholm, which took in the suburbs of Box Hill, Blackburn and Mount Waverly, because of the high proportion of Chinese speakers in the electorate.

The 2016 Census found about 20 per cent of Chisholm residents spoke Mandarin or Cantonese at home, compared with a figure of less than 4 per cent nationally.

Ms Liu won her seat with an ultra-thin margin of just 1,090 votes. She is the first Chinese-Australian woman to win a federal seat in the Lower House.

Mr Bradley said the cases hinged on not only proving that the posters were invalid, but they influenced the outcome of the election.

"We have to convince the court that it was likely to have affected the result. In Chisholm [the result] was knife-edge," he said.

Mr Frydenberg comfortably won Kooyong with a two-party preferred vote of 55.7 per cent.

The Greens candidate for Kooyong, Julian Burnside, who lost with 44.3 per cent of the two-party preferred vote, said the challenge should succeed.

"I think the challenge is correct. The signs were outrageous," Mr Burnside told the ABC.

"They basically instructed people in Mandarin, they said 'if you want to cast a valid vote you need to put a '1' beside liberal', and that's misleading, deceptive and wrong."

Mr Yates has launched a crowd-funding campaign for the legal action, which has so far raised more than $17,000.