This mobile billboard featuring the slogan "ditch the witch" has been driven around central Melbourne. (Supplied)
In short:
Premier Jacinta Allan has been joined by Prime Minister Anthony Albanese and former Prime Minister Julia Gillard and other politicians in denouncing the language used to describe her on political signs seen in the Melbourne CBD.
The mobile billboard featured an image of Ms Allan along with the phrase "ditch the witch", the same derogatory phrase used in 2011 about Ms Gillard.
Interspersed with the anti-premier slogans were sexually suggestive advertisements for Melbourne brothel Gotham City, which has said it was one of the businesses behind the campaign.
Victorian Premier Jacinta Allan says a mobile billboard seen in the Melbourne CBD featuring a doctored image of herself alongside the phrase "ditch the witch" is sexist and part of a "corrosive" political debate.
"A billboard truck using sexist language has been driving around Melbourne as part of a secret and well-funded political campaign," Ms Allan said on Sunday.
"People are entitled to disagree with me. That's democracy. But I care that this attacks women."
Melbourne brothel Gotham City confirmed it was involved with funding the campaign, along with many other businesses.
Gotham City was the target of a drive-by shooting in April during a spate of attacks on Melbourne hospitality venues.
A few of the billboard variations call on the premier to help businesses. (Supplied)
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The premier said political debate had become "corrosive" in the last few years and behaviour that once would have been condemned is now "just another part of life".
One of the ads features the likeness of the premier holding a jerry can, saying "let it burn to the ground Allan". (Supplied)
Ms Gillard released a statement saying she was "disgusted" by the use of the same slogan 15 years later.
"It was roundly condemned then. In the years since, my view has been that things were slowly improving for women in politics," she said via Instagram.
"I am saddened to see that improvement cast aside and this tired old trope resurrected."
Ms Gillard labelled those responsible for funding the anti-Allan signs "sexists" and called for the signs to be removed.
"Why should women and girls in Victoria be subjected to such visible misogyny?"
she said.
The truck's anti-premier ads are interspersed with ads for Melbourne brothel Gotham City. (Supplied)
The Victorian opposition said it was not behind the ad campaign.
Opposition Leader Jess Wilson said the sign was "sexist" and "inappropriate".
"That sort of language, that sort of discourse should never be used in politics," she said on Monday.
Former federal Nationals leader David Littleproud said the ads lacked intellect, but did not raise issues "of safety" for politicians.
"After 15 years, you think they would have come up with a new slogan," he told Sky News.
"This is something that's just really lazy … I don't think this progresses anyone's case."
'Sexism has no place in politics'
Other federal and state MPs have criticised the signs since yesterday, including Prime Minister Anthony Albanese.
"The sexist campaign targeting the Victorian premier is totally unacceptable and has no place in public life," he told reporters on Monday.
"You can have a disagreement with peoples' policy position, by all means. You don't have to denigrate people in such a personal way.
"Young girls will see that, you know, depiction of a premier as a witch, just like the denigration that Julia Gillard suffered from as prime minister, and it is just not on."
The Prime Minister strongly criticised the ad campaign targeting Jacinta Allan during a press conference on Monday. (ABC News)
Federal deputy Liberal leader Jane Hume on Monday echoed the prime minister and premier's statements.
"Sexism has no place in politics," she told Sky News.
"It's perfectly fair and reasonable to criticise a policy, it's perfectly fair and reasonable to criticise a party, it's perfectly fair and reasonable to criticise a politician, but you don't need to go to gender in order to do that."
One Nation leader Pauline Hanson was not sympathetic towards Ms Allan.
"Suck it up sweetheart, right, you've seen what's happened to me over the years," she said on Sunday.