Another in a string of bakeries to refuse to provide a wedding cake for a same-sex couple is being sued for doing so on religious grounds.

The couple, who were refused service by the bakery Sweet Cakes by Melissa, back in January, have filed a discrimination complaint, and a Government office has said it will investigate. The bakery turned down the couple citing their religious beliefs as the reason.

The Oregonian on Wednesday reported that the state Bureau of Labor and Industries will investigate whether the business indeed violated a 2007 state law protecting the rights of LGBT people in employment, housing and public accommodations.

The bureau said it is the tenth complaint in five years of discrimination in a public place based on sexual orientation or gender identity.

Religious organisations and parochial schools are exempt under the law, however private business owners are not allowed to discriminate based on sexual orientation.

Similarly, in June a gay couple in the US state of Colorado filed a discrimination lawsuit against a bakery, saying it refused to provide a cake for their wedding, and alleging a history of discrimination against same-sex couples.

A similar situation arose in 2011, when a lesbian couple from Iowa said they were unsure whether or not to pursue a civil rights complaint over the refusal of a Christian baker to make their wedding cake.