An anti-gay activist has filed a religious discrimination complaint against a bakery that refused to decorate a Bible-shaped cake with words describing homosexuals as 'detestable'.

Azucar Bakery in Denver, Colorado, agreed to the order last March but said they would not inscribe the incendiary words.

They also refused the elderly man's request for a design featuring two men holding hands with an 'X' over them, followed by the words 'god hates homosexuality'.

Refused: Marjorie Silva, owner of Azucar Bakery, refused to create a homophobic cake for a customer

Unperturbed, he suggested, instead, icing on anti-gay scripture and the ghostbusters logo.

Their refusal enraged the man, who threatened to involve his attorney.

When owner Marjorie Silva explained they could provide the man with icing and a piping bag to design his own decoration, he stormed out and took action.

If unresolved, the case could go to trial.

The controversy has emerged just days after the Supreme Court agreed to address same-sex marriage in Colorado this term.

Silva believes the man may have targeted their firm deliberately after she made pro-gay comments to a Spanish-speaking news agency.

Inclusive: She said she could make a Bible-shaped cake but would not ice discriminatory words or images

Targeted? Silva fears their firm may have been targeted by the man after she made pro-gay comments

'We make [Christian-themed] cakes all the time,' she told Out Front. 'No problem at all.'

'He wanted us to write God hates... just really radical stuff against gays.

'He wouldn’t allow me to make a copy of the message, but it was really hateful.

'I remember the words detestable, disgrace, homosexuality, and sinners.

'I told him that I would bake the cake in the shape of a Bible.'

Legal action: The firm now has two months to file a response to avoid a 'religious discrimination' court case

Now, the bakery has received an official complaint letter from the man via the Department of Regulatory Agencies (DORA).

Silva, who is filing a response, said: 'I would like to make it clear that we never refused service. We only refused to write and draw what we felt was discriminatory against gays.