Ben Summerskill, the chief executive of gay rights group Stonewall said:
"Many people will be pleased by today's decision.
"Had these voodoo 'gay cure' adverts appeared in the pages of the Spectator or the Daily Telegraph it's unlikely there would have been complaints.
"But in a city where over half of gay young people face bullying at school, and where tens of thousands of gay people are subjected to hate crimes every year just because of the way they were born, it's perfectly proper for a mayor to object to the use of such advertising in an iconic public setting."
More top news
Man who has barricaded himself in house for three days may have a stash of petrol and other explosives, police say.
Transport secretary Chris Grayling said MPs will decide this week about where to allow airport expansion in south east England
The Met Police has thanked residents in Northolt for their patience but has warned the armed stand-off could take time to resolve.