A giant poster brought into a Toronto FC game against the Montreal Impact Saturday night has left fans of both teams crying foul.

The poster depicted a man in the red colours of Toronto FC, with a woman wearing underwear in Montreal Impact blue kneeling in front of him, suggesting a sexual act. In bold letters, it had a phrase meaning "Montreal sucks."

"A big banner of a woman on her knees implying fellatio and the phrase 'Montreal you suck' is a disgrace," the Twitter user wrote, linking to a photo of the poster.

The Toronto club apologized to Twitter users who expressed their disapproval, saying the poster was unacceptable.

"Upsetting to say the least," the club wrote to one soccer fan.

"We will look into this. This is not OK."

<a href="https://twitter.com/girlsloveIMFC">@girlsloveIMFC</a> not okay by any means. We are looking into it. I'm sorry. —@torontofc

Official complaint coming

At least one Impact fan says she will file an official complaint with Major League Soccer.

Elizabeth Cotignola wasn't at the game but saw the poster being shared on Twitter.

"I perceived it not even as an Impact fan seeing it as a slight towards Impact fans but as a woman seeing it as sexist, misogynic imagery," she told CBC. "It made my blood boil."

Cotignola posted to Twitter that she would file a complaint and says she's received a lot of positive support.

<a href="https://twitter.com/hashtag/IMFC?src=hash">#IMFC</a> and <a href="https://twitter.com/hashtag/TFC?src=hash">#TFC</a> fans, if anyone wants to submit a formal complaint, I'll author one and send it to <a href="https://twitter.com/MLS">@MLS</a>. Let me know if you want to co-sign. —@LaDiavolina

"The reason I'd like this documented and formalized is because this isn't an issue that's specifically tied to this one incident, in this one fan base, in this one game," she said.

"It's been a problem across a lot of venues at Major League Soccer and other sporting venues. I think we're now really cognizant, in 2016, that sports is a fairly toxic domain for women."

Cotignola says the league has to take a firm stance on the issue of sexism.

CBC News has asked for comment from Toronto FC, the Montreal Impact and Major League Soccer, but has not yet heard back.