In what could be the first emoji gaffe in federal politics, Kate Ashmor, who is running for the Liberals in the ultra-marginal inner-city Melbourne seat of Macnamara, posted the emoji-comment on her personal Facebook.

Linking to The Sydney Morning Herald's 2017 article exposing the $60,000 Labor members shelled out for Mrs Shorten's makeover for the last campaign, Kate Ashmor, the Liberal candidate for the new seat of Macnamara in Melbourne, included lipstick, pig and thinking face emojis.

When asked if she was referring to the well-used phrase "You can't put lipstick on a pig," or if she had any other meaning by denoting Mrs Shorten with the pig emoji, Ms Ashmor said she was sorry and deleted the post. "I apologise for my post from two years ago," she said.

"My post was related to Bill Shorten and his character and policies, and no one else."

While not all political wives seek media attention, Chloe Shorten has established herself as a public figure. She has her own websites and social media channels, gives speeches and has released two books including her own cook book. She campaigns on gender equality and ending family violence and is associated with several not-for-profit organisations.

Nevertheless, politicians' wives are usually considered off-limits for attack in Australian politics and a gender-based attack is especially rare.

The figure of speech previously caused a political storm when Barack Obama said "you can put lipstick on a pig, but it's still a pig," at a rally during the 2008 US presidential election.

His political rivals took great offence at it, saying Mr Obama's comments had been directed toward the then Republican vice-presidential nominee Sarah Palin, who had previously remarked: "You know, the difference between a hockey mom and a pit bull? Lipstick."

The Republicans ran ads accusing the Democrats of sexism.