(CNN) From July, London commuters will no longer have to view advertisements that "conform to unhealthy or unrealistic body images," the city's transport authority announced.

Making good on his campaign promise, newly-elected mayor Sadiq Khan said all advertising on the city's transport network that is "likely to create body confidence issues, particularly among young people" will be banished.

"As the father of two teenage girls, I am extremely concerned about this kind of advertising which can demean people, particularly women, and make them ashamed of their bodies. It is high time it came to an end," Khan said Monday.

Last year, hundreds of complaints were made to the UK's Advertising Standards Authority over a poster on tube station walls showing a woman in a bikini with the words "Are you beach body ready?"

More than 70,000 people signed a petition calling for its removal but the regulator later ruled that the ad was "unlikely to cause serious or widespread offense."

'Our customers cannot simply switch off'

The ban on "unrealistic" advertising will affect around 12,000 ads in spaces controlled by Transport for London (TfL) -- including on the London Tube, overground trains, trams, buses, bus shelters and street advertising.

The transport body's advertising assets are the "most valuable in the world" according to TFL, and are worth £1.5 billion ($2.1 billion) in revenue over the next eight and a half years.

Graeme Craig, TfL commercial development director said advertising on the public transport system had a different responsibility to viewers than TV, online and print media.

"Our customers cannot simply switch off or turn a page if an advertisement offends or upsets them and we have a duty to ensure the copy we carry reflects that unique environment," Craig explained.

The announcement also established an advertising steering group which will monitor all ads it runs and look at better reflecting the full diversity of London, it said.