Signs telling voters in key electorates to put the Liberals first were designed to look like they came from the independent electoral commission, a key party figure admits.

The Chinese-language corflutes were posted at Melbourne polling booths, including the electorates of Kooyong and Chisholm, on election day in May.

When translated, the purple and white signs – in the colours used by the Australian Electoral Commission – say the “correct” way to vote is to put the Liberals first.

Failed Kooyong candidate Oliver Yates is challenging the re-election of Treasurer Josh Frydenberg and climate campaigner Vanessa Garbett is challenging the election of Gladys Liu in the neighbouring seat of Chisholm, alleging the signs broke the law.

“You intended to convey the impression that this was an AEC corflute, didn’t you?” Lisa De Ferrari SC, acting for the challengers, asked former Victorian Liberal Party director Simon Frost in court in Melbourne on Wednesday.

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

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

“Yes,” Mr Frost replied.

It came after he said the messages on the signs, displayed at seven Melbourne electorates in both simplified and traditional Chinese script, were different to what had been approved by the party.

“The translation was not as I had given … as it was re-translated back through the media,” Mr Frost told the court.

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

Mr Frydenberg and Ms Liu knew about the corflutes and allowed them to be displayed, Ms De Ferrari told the court.

She is seeking the “drastic measure” of voiding the MPs’ elections.

“The principle, we say, is also important and too important to have those considerations of practical inconvenience take over,” Ms De Ferrari said.

The AEC has denied the posters were likely to mislead or deceive voters into thinking they were official instructions from the commission.

It urged the court to throw out the cases.

amazing moment in the court of disputed returns, pivotal moment in @JoshFrydenberg/@GladysLiuMP deceptive signs case brought by @_Oliver_Yates.

then acting @LiberalVictoria state director, & now josh’s chief of staff, admits signs deliberately impersonated @AusElectoralCom! https://t.co/IapJ65f1u9

— 💧simon holmes à court (@simonahac) November 6, 2019

Outside court, Mr Yates said the case showed the AEC had “failed dismally”.

“The idea that we have political parties engaged in misleading and deceptive conduct at election time is appalling,” he told reporters.

“There should be no need for a case like this. We shouldn’t have to be running this case, the AEC should be running this case.”

Mr Frost declined to comment as he left court.

-AAP