Sadiq Khan has been put on the spot over Transport for London’s decision to allow adverts on Tube trains and buses depicting a controversial Islamic preacher holding a briefcase containing US dollars in flames.

The transport authority, which is overseen by Mr Khan, was urged by former Conservative London Mayoral candidate Susan Hall to reconsider its decision to display a series of billboards promoting Islamic finance startup Wahed, which encourages commuters to “withdraw from exploitation”.

The controversial adverts show Muslim preacher and motivational speaker Ismail ibn Musa Menk, who is also known as Mufti Menk, surrounded by images of burning US dollar notes.

One shows Menk clutching a silver briefcase filled with burning cash, accompanied by text suggesting charging interest on loans was once considered “exploitation” and claiming this practice has contributed to a “massive wealth gap”.

Seven years ago, Mufti Menk was banned from entering Singapore, with the city-state’s Ministry of Home Affairs accusing him of promoting “segregationist and divisive teachings”. Denmark has also barred his entry.

However, Majlisul Ulama Zimbabwe, an Islamic school which is associated with Menk, defended him, insisting the ban is based on “an inaccurate perception” of one of his lectures and claiming he maintains “good relations with leaders and people of other faiths”.

In 2013, several UK universities scrapped Menk’s speaking engagements after it emerged that he had previously branded gay people “worse than animals”. Menk later retracted his remarks.

Speaking at the London Assembly earlier this week, Ms Hall told Mr Khan: “You’ll be aware of the very, very strict rules around food.

“In fact, you’ve been commenting on it just now, and so strong are these rules that Ed Gamble, a comedian, I’m sure you know, had to Photoshop out a hot dog and replace it with a cucumber in an advert for his show.

“However, you’ve got a company called Waheed, who’s a finance company, and featuring on those adverts is a chap called Mufti Menk, who actually is known to have denounced homosexuality as filthy and said that gays were worse than animals. So you’ll stop a hot dog being put on there. You’re quite happy to have people like that, featuring in those adverts.”

Mr Khan replied: “I’ll look at it as soon as Mayor’s Question Time is finished, to see what’s going on there. I am more than happy to do that and get back to the member.”

Ms Hall said: “Please do because I think things like that just make the whole thing look totally ridiculous.”

TfL faced accusations of censorship earlier this year after blocking an advert by Muzz Social, which claimed that social media was “killing Muslims”. Muzz Social, the world’s largest social media platform for Muslims, tried to run provocative ads with slogans like “Muslims have no place online” and “the algorithm hates Muslims”.

TfL blocked the campaign, saying it was likely to cause “widespread or serious offence to reasonable members of the public”.

Ayesha Malik of Muzz Social defended the campaign, insisting it was intended to raise awareness of issues faced by millions of Muslims.

A TfL spokesperson defended the Wahed advert, stating: “This advert was reviewed and complies with our advertising policy, which reflects legal requirements. The Mayor is not involved in approving or deciding which ads run on the TfL network.”

A spokesperson for the Mayor of London’s Office said: “The Mayor is clear that there is no place for hate in London and he strongly condemns any language which divides London’s amazing diverse communities. The Mayor has no involvement in approving or deciding which ads run on the TfL network, and TfL’s policy reflects legal requirements.”

Express.co.uk has contacted Wahed for comment.