Core Issues Trust has lodged papers at the High Court attempting to force Transport for London to remove hundreds of new pro-gay equality posters on the capital’s buses via an injunction.

Stonewall, Britain’s largest gay rights charity, has resumed its advertising campaign of placing its “Some people are gay. Get over it!” posters on buses throughout London and remains unfazed by the latest threat from the anti-gay Christian group.

In April 2012 Core Issues Trust tried unsuccessfully to advertise posters advocating gay-to-straight conversion therapy in a direct response to Stonewall’s pro-gay posters.

The Trust’s slogan read: “Not Gay. Ex-Gay, Post-Gay and Proud. Get over it!”

Although the ad campaign was passed by the Committee of Advertising Practice, Mayor of London Boris Johnson instructed Transport for London (Tfl) to pull the campaign before it could run – just days before the 2012 Mayoral Election.

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

Core Issues Trust  attempted to challenge the TfL decision – but in March the High Court declared it was not unlawful.

However, Mrs Justice Lang ruled that TfL’s process in introducing the ban “was procedurally unfair, in breach of its own procedures and demonstrated a failure to consider the relevant issues”.

But that was outweighed by factors against allowing the ad, including that it would “cause grave offence” to those who were gay and was perceived as homophobic, “thus increasing the risk of prejudice and homophobic attacks”.

Core Issues Trust has since appealed the ruling and has now lodged an urgent judicial review application seeking an injunction forcing TfL to take down the new Stonewall posters.

Dr Michael Davidson, founder of Core Issues Trust, said in his application: “I feel that Stonewall and the defendant are deliberately flouting the rulings of the court by renewing their advertisement campaign on buses which was clearly prohibited by the earlier judgment of Mrs Justice Lang.”

He added: “Until such time when we have the judgment of the Court of Appeal, the defendant should not have allowed Stonewall’s advertisement to reappear on their buses.”

On Thursday, a spokesman for TfL replied: “These ads are in line with our advertising policy.”

Ben Summerskill, chief executive of Stonewall, said: “It does seem a tragedy that these people who make so much noise about being Christian don’t spend a little more of their money on tackling polio or Third World poverty but a lot of money on slightly frivolous legal actions.”