Online casino company 888.com will withdraw adverts from locations including London’s transport network after a backlash against their tone, prompting criticism of the capital’s mayor, Sadiq Khan, for allowing them to appear in the first place.

With less than a week to go before Londoners vote for their next Mayor, Khan’s Conservative rival, Susan Hall, joined a leading clinician and a group of peers in questioning Transport for London’s “baffling” decision to accept the campaign.

TfL has previously blocked promotions featuring artisanal cheese, a poster for a play that depicted a Victoria sponge cake, and the Wimbledon tennis tournament’s famous strawberries and cream, on the grounds that they promoted unhealthy eating.

But despite Khan’s 2021 manifesto pledge to ban gambling ads on London’s transport network, TfL has continued to accept promotions for bookies and online casinos, pending an independent review of the links between advertising and gambling harm.

In recent weeks, 888.com had launched a campaign on the London Underground, trains and buses, featuring slogans such as: “This carriage is now a casino”. Some black cabs carry the slogan “Fancy a spin?”

But on Friday, after a request for comment from the Guardian, 888.com confirmed it would withdraw some of the ads, although it did not say which ones. It said the ads “could be interpreted in a different manner to the brand position we aim for”.

The decision is thought to be a response to criticism of the tone in which the ads promote online casino games, which are associated with higher rates of harm than most other gambling products, according to NHS survey data.

TfL said the 888 ads complied with the advertising regulator’s broadcasting code and its own policies, including that the ads should not “trivialise gambling”.

Khan’s closest rival for the Mayor, Hall, said: “Sadiq Khan’s inconsistency in what adverts he allows and what ones he bans is baffling for Londoners.

“He is […] banning adverts featuring cheese or strawberries and cream, while being completely relaxed about vaping and gambling?

“We need a common sense, clear approach to this, not one that allows the mayor […] to play favourites.”

Professor Henrietta Bowden-Jones, who oversees the National Problem Gambling Clinic and is recognised as one of Britain’s leading experts on addiction, also criticised Khan after seeing one of the ads on the Tube.

In a letter to TfL’s commissioner, Andrew Lord, the House of Lords group Peers for Gambling Reform said the “aggressive” ads contradicted Khan’s manifesto pledge.

The group’s chair, Lord Foster, said TfL’s stance on gambling, relative to junk food ads, was “clearly inconsistent”.

TfL’s review of its policy on gambling ads has allowed firms including 888.com, which is chaired by Labour peer Lord Mendelsohn, to launch high-profile campaigns. Gambling firms have paid nearly £1.8m over the past two years to advertise on the network.

888.com has received some of the largest fines in the history of the British betting industry, including a £9.4m penalty in 2022 for multiple failings that led to customers racking up huge losses during the depths of the Covid pandemic.

In 2017, it was fined £7.8m, then a record penalty, for similar failings. It also owns William Hill, current holder of the record for the highest ever penalty meted out by the Gambling Commission, a £19.2m penalty issued in 2023.

While TfL accepted 888’s ads, it has previously banned images promoting food that is considered unhealthy because it is high in fat, sugar or salt.

Ads deemed beyond the pale included one featuring artisanal cheese and a promotion for the Wimbledon tennis championships that included strawberries and cream.

Comedian Ed Gamble was also forced to replace a hotdog in a poster for his tour, titled Hot Diggity Dog. Gamble opted for a cucumber instead.

More than 80 councils across the UK have taken some form of action to restrict gambling advertising.

A London Labour spokesperson said: “City Hall commissioned an independent review of existing research on harmful gambling to help develop understanding of this subject. Further policy work is under way, and will be considered carefully by Sadiq if he is re-elected on 2 May.”

An 888 spokesperson said: “We continuously listen to feedback regarding the effectiveness of our advertising campaigns and acknowledge that, whilst fully compliant with all advertising regulations and standards, our latest campaign could be interpreted in a different manner to the brand position we aim for.

“As a result, we have decided to change the focus of this campaign and are withdrawing certain adverts that are currently running.”