An Australian couple who believe homosexuality is a sin that can be overcome are in a court battle with a West Australian organisation which denied their application to become foster parents.

Christians Byron and Keira Hordyk, from Perth claim Wanslea Family Services discriminated against them on the grounds of their religious conviction.

The couple, who have their own children, took their claim to the Equal Opportunity Commission but were turned away as the commissioner who found the complaint lacked 'substance', WAtoday reported.

The Hordyk’s said they could love a child in the same manner they care for their birth children, they said an LGBTQI identification was a sin they would help the child overcome.

In September last year, the couple received a letter from Wanslea explaining their application would not go further. 

An initial report from Wanslea suggested the Hordyks would be suitable carers. 

The Hordyks' opinions on LGBTQI issues did not meet the 'providing a safe living environment' competency specified by the Department of Communities, the letter said.  

The couple argue they were discriminated against because their application was denied over their religious beliefs. 

They believe Wanslea could still approve them as foster carers for children who do not identify as LGBTQI.