It's the shop with a hip reputation for cutting-edge clothes and funky homewear, but Urban Outfitters is facing a backlash – and even a boycott – over a slogan T-shirt.

The chain, which has more than 100 outlets in the US and nine in Britain, is under fire from gay rights campaigners after the company removed T-shirts bearing the slogan "I Support Same Sex Marriage" from sale – a decision that is being seen as the latest example of international companies bowing to pressure from right-wing US groups.

This increasing influence – via websites and targeted email – is a cause for concern in Britain's gay community. "This shows a very worrying trend – special interest groups in the States affecting another country with a completely different culture," said Joseph Galliano, editor of Gay Times.

"There are insidious and increasingly loud religious right-wing Christian evangelical lobby groups that are pushing their beliefs down everyone else's throats," he said.

Urban Outfitters has previously come under fire from gay rights organisations because of the conservative views of its director, Richard Hayne. Mr Hayne has donated money to the campaigns of former Republican senator Rick Santorum, who has equated homosexuality with paedophilia and incest. Mr Hayne refuses to be drawn on his own views on homosexuality, saying to the Philadelphia Weekly in 2003: "I have my own opinion, but I am not going to share it. Our job as a business is not to promote a political agenda."

While Urban Outfitters refused to comment on why it had removed the T-shirt from sale, its designer, Tara Littman, said that she had been told that the range had been pulled from both US shops and the website because of "bad press" and "bad sales".

"There was no evidence of this bad press, except one Christian blogger who complained," said Ms Littman, who is selling the shirts through her label Support Shirts. "There was no proof of bad sales either. They didn't tell me that they had been removed until weeks later," she added.

The T-shirts were taken off shelves in California five days before the state voted in favour of Proposition 8 on 4 November, which saw gay marriage abolished. Lesbian and gay couples can marry in just two US states, Connecticut and Massachusetts.

"The decision to remove this T-shirt is as eccentric as a similar decision by Heinz to withdraw an innocent TV advert," said Ben Summerskill, chief executive of the gay rights organisation Stonewall, referring to his call earlier this year for shoppers to boycott Heinz, after the firm dropped a TV ad featuring two men kissing, which prompted more than 200 complaints to the broadcasting watchdog Ofcom.