Footage shot by a woman walking past the van parked outside Senator Seselja's electoral office on Thursday night showed two posters inside of two ACT Greens candidates, Christina Hobbs and Carly Saeedi.

The poster of ACT Greens Senate candidate Christina Hobbs had been vandalised to depict her with several teeth blacked out and a moustache.

A speech bubble duct-taped next to her said: "I need a light railing".

While Senator Seselja said he was unaware of the posters and unequivocally condemned them, Ms Hobbs said the word "railing" was slang for term for violent sex and was often associated with rape.

"When you put your hand up to run for parliament you are told to expect a certain level of potential harassment. When you're a female candidate you understand it's going to be particularly vile and often sexual in nature. But what you don't expect, is that your male political opponent is somehow going to be 'in on the joke' - busing around a group of young men who seem set on harassment and intimidation," Ms Hobbs said.

"There is no way that the Senator can deny seeing these images, this is his campaign bus, parked outside his campaign office. Many of us have seen him getting in and out of this van over the past week and whether he was in the front seat or the back seat, these pictures stuck to the dashboard would have been hard to miss."

But Senator Seselja said the first he knew of the posters was when media contacted him for comment on Friday morning.

Ironically, the vandalised posters came to light the day Ms Hobbs planned to unveil a policy to reduce violence against women and support domestic violence survivors.

Senator Seselja also promotes himself as a White Ribbon ambassador on his website.

"When what we all know, is that ending violence requires a cultural change that is supposed to start at the top. Here in Canberra, we're clearly scraping the bottom," Ms Hobbs said.

"I'm sure this was all intended as a joke, but in 2016, it's just not funny."

The condemnation was swift and swingeing on social media.

It isn't the first time the senator's van has landed him in hot water in the past few days.

Voters have also accused Senator Seselja's staff of parking the van in loading areas illegally, although Parkings Operations have clarified non-commercial vans can park in loading zones if they have the right permit.

Canberra Liberal campaigners also sparked furore in 2012, when then Chief Minister Katy Gallagher's staff had to call police after she was allegedly pursued by two car loads of young male Liberals while she was campaigning in southern Canberra.

Ms Gallagher said the vandalism was "simply appalling and cannot be excused or ignored by Zed Seselja"

"He should immediately apologise to Christina Hobbs and explain exactly why this material, openly and violently degrading a female candidate was in his campaign bus," she said.

"Canberrans expect better standards from those who seek public office and from the volunteers who work on their campaigns."

The senator told the ABC on Friday afternoon his campaign volunteers were responsible for the material.

He described the vandalism as "juvenile sorts of jokes".

"I certainly apologise for any offence," he said.