The Australian Electoral Commission (AEC) has told a court it is "implausible" that purple Chinese-language placards put up by the Liberal Party drastically affected the federal election result in Victoria.

Key points: The signs, which resembled AEC material, told voters to preference the Liberal Party first

The signs, which resembled AEC material, told voters to preference the Liberal Party first A lawyer representing a challenge to the election results in Chisholm and Kooyong argued the signs targeted specific voter groups

A lawyer representing a challenge to the election results in Chisholm and Kooyong argued the signs targeted specific voter groups But the AEC argued the use of purple was not enough to influence people

"It is hard to imagine any adult citizen being so naive and gullible to think Australia is a one-party state," AEC solicitor James Renwick said.

The Court of Disputed Returns, which is sitting in the Federal Court in Melbourne, is being asked to unseat Federal Treasurer Josh Frydenberg and his Liberal colleague Gladys Liu for allegedly using misleading signs during the May election.

The signs, known as corflutes, which resembled the purple colours used by AEC, were posted at 13 polling stations in Mr Frydenberg's seat of Kooyong and 29 polling booths in Ms Liu's seat of Chisholm.

These posters were placed next to an AEC flag at a voting booth in Chisholm. ( ABC News: Gemma Hall )

Some of the signs, which were written in Chinese, instructed voters of "the right way to vote" and told electors to put a "1" by the Liberal candidate's name.

Unsuccessful independent candidate for Kooyong, Oliver Yates, and Chisholm voter Vanessa Garbett have taken the case to court and petitioned for the results to be declared void.

But the AEC solicitor told the court in his submission that the decision to declare an election void was "drastic" and the onus was on the petitioners to prove the actions greatly affected the outcome.

"This theory put forward that there were waves of Chinese voters that came to Chisholm and Kooyong not knowing who they were going to vote for, and saw this incredible sign, which no ordinary elector could have acted on, and that they were affected or mystified … it is just an assertion and it is not enough," Dr Renwick said.

On Wednesday, senior Victorian Liberal Party figure, Simon Frost, admitted in court that the Chinese-language signs were designed to convey the appearance of official electoral commission material.

Mr Frost, who was the party's acting Victorian director at the time, admitted the signs did not have Liberal Party logos, and were in purple and white, the same colour scheme used by the AEC.

Campaign 'extensive' and 'targeted', court told

Former Liberal Party member Oliver Yates ran as an independent candidate in Kooyong. ( ABC News: Karen Percy )

The lawyer representing Mr Yates and Ms Garbett, Lisa De Ferrari, argued in her submission that the corflutes were "specifically targeted".

"Advertisers do not spend money on things that they do not think are effective," she said.

"This is not a case of a few isolated incidents of how to vote cards. This is extensive.

"The corflutes were planned weeks in advance and targeted at specific groups.

"With knowledge that the result in Chisholm was tight."

She said the proportion of people who speak Mandarin or Cantonese in Chisholm was 40 per cent in 2016 and 12 per cent in Kooyong.

But Mr Renwick said the use of the purple colour itself was not enough and the subset of voters which could have been targeted and swayed by the signs was not sufficient.

"[The signs] did not have an AEC logo," he said.

"And given it was in Chinese script only, the number of people who speak Chinese, be it Mandarin of Cantonese, but no English in the home is too small to have an effect."

Ms Liu defeated Labor's Jennifer Yang in the seat of Chisholm by 1,090 votes on a two-party preferred basis.

One in five people in the electorate claim Chinese ancestry.

Josh Frydenberg won his seat comfortably over Greens candidate Julian Burnside, but did not win on first preferences.