Pauline Hanson’s candidate in the byelection for Sussan Ley’s seat likened former prime minister Julia Gillard to a “non-productive old cow” that should be destroyed before suggesting the comments were tongue-in-cheek.

Agriculture businessman David Farley was picked on Saturday as the One Nation candidate for the 9 May byelection for Farrer, which Ley held for 25 years.

The race – a critical first test of the party’s surging public support, and of the Liberals under Angus Taylor – was triggered by Ley quitting parliament last month after being ousted as Liberal leader.

Farley, 69, is a Narrandera-based irrigator, a father of three daughters and grandfather of seven.

As the chief executive of the Australian Agricultural Company in 2012, he made a reference to the then Labor leader as he spoke about cows being destroyed using new abattoir technology.

“This plant is designed to process old cows,” Farley told a business conference, referring to a plant under construction which was designed to kill older cows to produce cheap meat, adding value for farmers from ageing cattle.

_{Sign up: AU Breaking News email}

“So the old cows that become non-productive, instead of making a decision to either let her die in the paddock or put her in the truck … this gives us a chance to take non-productive animals off and put them through the processing system.

“So it’s designed for non-productive old cows. Julia Gillard’s got to watch out.”

Media reports said the comment was met with sustained laughter from the audience.

Farley claimed at the time the comments were meant to be “tongue-in-cheek” and had been taken out of context.

He was selected as One Nation’s candidate for Farrer on Saturday, at an announcement event at which Hanson and Nationals defector Barnaby Joyce were present.

Gillard faced repeated sexist commentary as the country’s first female leader. Joyce attended a notorious rally outside Parliament House in 2011, when Coalition figures, including the then opposition leader, Tony Abbott, stood in front of signs with Gillard’s likeness and the slogan “ditch the witch”.

Hanson defended her candidate on Sunday, telling Guardian Australia in a statement that the comments were “mild” compared with what the agriculture industry felt at the time.

“Get over it. This is a country with serious issues on our plate and journalists want to trawl through 14-year-old, tongue-in-cheek comments?” she said.

“I fully back David Farley and his comments.”

Hanson said the public should reflect on why the comments were made, which was in the context of the then Labor government banning live cattle exports to Indonesia for six months. That decision was later challenged in court by a cattle industry class action in 2020 and was ruled invalid.

“I’d suggest the comments were quite mild compared to what the industry truly felt at the time,” Hanson said.

The Liberal shadow minister for women, Melissa McIntosh, called the comments “inappropriate”.

“Mr Farley’s comments about former prime minister Gillard were inappropriate. It is up to Mr Farley to clarify those remarks,” she told Guardian Australia.

Ley held the southern New South Wales seat for 25 years, after nabbing it from the Nationals when former leader Tim Fisher retired from politics in 2001.

The Liberals are yet to nominate a candidate, while the Nationals are due to finalise preselection on Sunday.

Labor is not expected to run. Hanson claimed on Saturday that the prime minister, Anthony Albanese, did “not want to be shown up to be on the downward slope”.

“He knows damn well that he is going to get a lower vote than last time.”