An anti-gay campaign scheduled to begin Monday has been blocked by London transport officials.

Core Issues Trust and Anglican Mainstream, two Christian groups which believe gay men and lesbians can and should alter their sexuality, are behind the advertisements set to appear on five popular bus routes in the capital.

“Not gay! Post-gay, ex-gay and proud. Get over it!” the bus campaign was to say.

London Mayor Boris Johnson, who chairs Transport for London, pulled the advertisements amid public outrage, the AP reported.

“London is one of the most tolerant cities in the world and intolerant of intolerance,” Johnson said Thursday. “It is clearly offensive to suggest being gay is an illness someone recovers from and I am not prepared to have that suggestion driven around London on our buses.”

Mike Davidson, co-director of Core Issues Trust, decried the move as censorship.

“It is of deep concern that there can only be one point of view and that is the point of view of individuals who are determined to push through gay marriage and apparently believe that homosexuality cannot be altered in any possible way,” he said. “This is a disturbing development.”

The advertising campaign was cleared by the city's Advertising Standards Authority.