London mayor Sadiq Khan has ordered the removal of adverts declaring Israel "a racist endeavour" from bus stops across the city.
Several of the posters appeared across the capital the day after the Labour Party adopted the full International Holocaust Remembrance Alliance definition of anti-Semitism.
The definition says that "claiming that the existence of a State of Israel is a racist endeavour" could be considered an anti-Semitic act.
A group calling themselves "London Palestine Action" tweeted photographs of the adverts at various bus stops this afternoon.
A spokesperson for the London mayor said: "These offensive adverts are not authorised and are acts of vandalism which Transport for London and its advertising partner takes extremely seriously. They have instructed their contractors to remove any posters found on their network immediately."
TfL confirmed to BuzzFeed News they were working to remove the posters.
A spokesperson said: "These adverts are absolutely not authorised by TfL or our advertising partner JCDecaux. It is fly posting and therefore an act of vandalism which we take extremely seriously. We have instructed our contractors to remove any of these posters found on our network immediately.”