Surrogate says she knew Gammy’s biological parents didn’t want him

Baby Gammy is just seven months old and too young to know that he's at the centre of a surrogacy scandal.

The West Australian couple accused of abandoning the now 7-month-old baby deny leaving him behind and taking his healthy twin sister home.

They claim they've just found out Gammy exists and they don't believe he's their child.

They baby daughter was born to a Thai surrogate and they have showed Nine News the girl's birth certificate which shows both she and Gammy have the same birthday.

They also claim they didn't know she was a twin but surrogate mother Koy Chanbuan says that's not true.

She's disappointed with their reaction to the news.

The father admitted having trouble with the surrogacy agency in Thailand, which he claims no longer exists.

Surrogacy advocates want an overhaul of Australian laws which they've described as ‘flaky’. They blame that for driving more and more people to a surrogacy haven like Bangkok.

Around 400 children are born to Australian parents in Thailand each year.