The former acting Victorian state director for the Liberal party has admitted in court that signs written in Chinese at polling booths on election day were designed to look like official Australian Electoral Commission signage.

The full federal court is hearing the challenges to the elections of Liberal MP Gladys Liu in Chisholm and the treasurer, Josh Frydenberg, in Kooyong over three days. The cases have been brought against the two candidates by climate campaigner Vanessa Garbett and unsuccessful independent Kooyong candidate Oliver Yates.

On Wednesday, Simon Frost, who authorised the signs, said under questioning from Lisa De Ferrari, the barrister for the applicants, that the two signs – one in traditional Chinese characters, and one in simplified Chinese characters – were intended to appear as though they were AEC corflutes.

Facebook Twitter Pinterest Chinese language signs in Australian Electoral Commission colours in the electorate of Chisholm on the day of the federal election. Photograph: Twitter/Luke Hilakari

The signs that were used in seven electorates in Victoria said, according to an English translation, that the “correct way to vote” was to put 1 next to the Liberal candidate.

“You intended to convey the impression that this was an AEC corflute, didn’t you?” De Ferrari asked.

Frost, now an adviser to Frydenberg, took a long pause before replying: “It was similar to the AEC colours, yes.”

“So the answer to my question is yes?” De Ferrari pressed.

“Yes,” Frost replied.

Frost had already confirmed that the signs were intended to say “to make your vote count” but the meaning was lost in translation to “the correct way to vote”. He said on Thursday it “could be” a problem that the signs said different words than he authorised.

He also conceded he had not thought at the time about whether the signs were likely to mislead or deceive voters.

He told the court that the signs were proof-read the day before the election in May but the mistake was not picked up. He indicated the Liberal candidate for Hotham, George Hua, also proof-read the signs before the election.

On the day of the election, Frost said he became aware of concerns about the signs once the AEC tweeted replies to people raising issue with the signs, but decided the Liberal party’s opponents were merely making a political point out of the signs.

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He said at no point on election day did Frydenberg or Liu contact him about the signs, and there would have been no time to print off and distribute more than 500 of the new signs with the correct wording through seven Victorian electorates on election day.

De Ferrari said the ruling being sought is to void the election result in both electorates, causing byelections, which would come at a cost, but the principle was more important.

“[It] would put a stop to a developing and illegal practice that is really troubling,” she said. “The principle is too important to have those considerations of practical inconvenience take over.”

The hearing continues.

• This story was amended on 7 November 2019 to correct the name of the petitioner Vanessa Garbett. The petition was originally lodged under a different name.