British Kim Walmsley, who emigrated to Australia in 2004, only found out about the mistake when she recently applied to change her family's four-year visa to permanent ones.
The mum-of-five was devastated to discover this means that she is illegally locked in a "gay" marriage with her husband of 23 years, Jack, 49. The marriage was confirmed as illegal in a letter from the Archbishop of Canterbury in June last year.
Despite thinking this would be an issue they could quickly rectify, officials have insisted that the papers can't be amended and Kim, 49, and her family have had to return to the UK to try to resolve the issue.
Costs of the move and attempting to correct the blunder have cost a huge £150,000 and the General Register Office has admitted they are unable to fix the paperwork - despite accepting the mistake.
The family are currently staying in Liverpool and have even been subjected to vandalism - with homophobic graffiti scrawled over their home.
Kim was quoted in the Daily Mirror talking about the mix-up: "It's disgusting. I've lived nearly 40 years not realising I was registered as a boy, then my life fell apart. My marriage is a farce."
Local MP Bill Esterson has written to Prime Minister David Cameron in a last hope to get Kim's birth certificate changed.
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