The US Supreme Court has refused to hear an appeal by a Christian florist who was fined for refusing to provide wedding flowers for a same-sex couple.

The customer had been buying flowers for years from Barronelle Stutzman but when he asked her to do the arrangements for his wedding to another man, she declined because of her religious beliefs about marriage being between a man and a woman. 

She was handed a fine of $1,000 by a county court in Washington state in 2015.

In 2017, Washington state's Supreme Court ruled against Stutzman, but that decision was then voided by the US Supreme Court a year later. 

The Washington Supreme Court was asked to reconsider Stutzman's case following the verdict in favor of Christian baker, Jack Phillips, who refused to make a cake for a gay wedding. 

But when the Washington Supreme Court heard Stutzman's case again in 2019, it unanimously upheld its original verdict which concluded the florist had discriminated on the basis of sexual orientation. 

The Alliance Defending Freedom, which has been representing Stutzman in the case, said it was disappointed by the decision of the US Supreme Court not to hear an appeal.

"Barronelle Stutzman kindly served a gay customer for YEARS before declining to make art for a ceremony that's sacred in her religion. She was sued & persecuted for acting on deeply held beliefs," it tweeted.

"SCOTUS' decision not to hear this case is disappointing –– but our fight isn't over."

Stutzman's legal counsel, Kristen Waggoner, said the decision was "tragic".

"[T]he critical work of protecting the First Amendment freedoms of all Americans must continue," she said, according to CNN.

"No one should be forced to express a message or celebrate an event they disagree with."