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
Every Christmas gets a bit more desperate for one dog at Battersea. Can you help?
The problem has meant that no trains are able to run through Gatwick Airport rail station in West Sussex.
Schoolchildren found Eragon wearing a Christmas jumper in the bag filled with dog food, treats and a tear-jerking note, in a church.