Sadiq Khan has condemned adverts put up on bus stops describing Israel as "a racist endeavour", calling them "offensive".

Bus stops across London were defaced on Wednesday with anti-Israel posters mocking the International Holocaust Remembrance Alliance (IHRA) definition of antisemitism, after Labour finally announced it would adopt it, albeit with a significant caveat.

The London mayor said the "offensive" adverts were “not authorised” and were "acts of vandalism".

He said: “Transport for London and its advertising partner takes this extremely seriously. They have instructed their contractors to remove any posters found on their network immediately."

At least four different sites – Elephant and Castle, Waterloo Bridge, Bloomsbury and Westminster, across the road from Parliament itself, had advertising hoardings on bus stops fly posted with posters saying “Israel is a racist endeavour”.

This refers to one of the examples of contemporary antisemitism given in the IHRA definition of Jew-hate, which says calling "a state of Israel... a racist endeavour" could amount to Jew-hate.

A spokesperson for the Labour Party said: "This material hasn't been created or endorsed by the Labour Party"

JC Decaux, the advertising firm which owns a number of the defaced hoardings, confirmed that this was “vandalism – not advertising”, and that it had reported the bus stops in question and they would be “reposted soon.”

Saul Schneider spotted one of the posters, which were put up by campaign group LDNPalestineAction, on a bus stop in Southampton Row, Bloomsbury.

He told the JC he was “totally shocked to see this slogan on a billboard in central London.

“I see it as clear evidence that Labour’s inability/unwillingness to deal with antisemitism gives credibility to these views. So worrying that people just walk by and take it in.”

He reported it to the company that owns the site but said he had heard nothing back, and is hoping the police will take action.

James Robertson told the JC he had seen one in Elephant and Castle, while on his lunch break.

“I was struck by it and obviously I thought this is a result of all the stuff in the news yesterday," he said.

"It must surely be a response from somebody who is dissatisfied with the Labour party adopting the full definition of antisemitism.

“I’m sure it’s gone up overnight. I think it’s very sad that the next day you get people putting up posters that are clearly inflammatory.”

A Transport for London 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.”