The Australian parents of a surrogate baby boy who it was claimed they had abandoned because of his disability say they wanted him.

The story of seven-month-old Gammy made headlines around the world after it was claimed by his Thai surrogate mother, Pattharamon Chanbua, that the Australian couple she had carried him for had abandoned him and taken only his healthy twin sister back with them. 

But David and Wendy Farnell deny her claims and have previously said they did not know their daughter, named Pipah, had a brother. 

Speaking to Australia's Channel Nine this week, the couple again suggested 21-year-old Pattharamon was lying and that they had wanted to take Gammy too. 

"We did not abandon our son," they said.

"The surrogate mother - it is her choice if she wants to give you the baby or not give you the baby. Although you have a surrogacy agreement, it really doesn't mean anything. It is her decision, and our surrogate mother said that she wanted to keep the baby boy."

In addition to Down's Syndrome, Gammy is in need of medical treatment for a congenital heart condition.  

Pattharamon claims the couple urged her to have an abortion after finding out about Gammy's condition four months into the pregnancy.

On Channel Nine's 60 Minutes interview, the couple denied this.  

Asked if they abandoned Gammy, they said: "No, we never abandoned him. We never said to the surrogate mother to have an abortion. There is always hope." 

However, Mr Farnell, who was reportedly previously convicted for child sex offences, said the couple would have "probably" terminated the pregnancy if they had known sooner about Gammy's condition. 

One charity, Hands Across the Water, has so far raised $240,000 for Gammy's care, and the Daily Telegraph reports the donations will also go towards a new home for his surrogate mother and family.