Two Christian groups which believe gay men and lesbians can and should alter their sexuality are launching an advertising campaign in Britain.

According to the Guardian, the group Core Issues Trust will promote its message on London buses. The campaign is also supported by Anglican Mainstream, whose supporters have previously equated being gay with alcoholism.

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

The campaign is set to roll out on Monday and will appear on five popular bus routes in the capital.

Mike Davies, who heads Core Issues Trust, has previously stated that “homoerotic behavior is sinful.”

The Christian groups have previously accused gay rights supporters of promoting the “false idea that there is indisputable scientific evidence that people are born gay.”

Ben Summerskill, who heads Stonewall, Britain's largest gay rights advocate, labeled the ads “homophobic.”

“The only reason some gay people might want to stop being gay is because of the prejudice of the people who are publishing the ad,” he told the paper.

The campaign arrives as a highly-touted 2001 study which claimed that “highly motivated” gay people could alter their sexuality has been repudiated by its author, Dr. Robert Spitzer.

Spitzer told the American Prospect that such therapy “can be quite harmful.”

Summerskill added: “The promotion of this voodoo therapy is hugely irresponsible given the damage that it appears to do to some people.”