The quasi-adoptive parents of a two-year-old girl have been forced to return their daughter to her biological parents despite having raised the toddler since birth.

The couple — known as Ms Blaze and Ms Darnley — had an informal adoptive arrangement with the birth mother Ms Grady, who decided during her pregnancy in 2012 that she would relinquish custody of her daughter after the birth.

Over a seven day trial in Brisbane, the Family Court heard the biological mother’s decision was based on her belief the child’s father would not be able to provide financial assistance to the newborn or her three other children, who are now aged 19, 11 and 10.

However, DNA testing undertaken after the birth established the man Ms Grady suspected to be the father was not the biological parent, and it was later determined that another man, Mr Harper, was in fact the father.

Justice Michael Kent delivered his judgment in the Family Law Court, ordering the biological parents of the girl — known as “B” — be given shared parental responsibility as it was in her best interests.

Ms Grady had been a long term friend of Ms Blaze, and the couple resided with Ms Grady from February 2013 until the child’s birth in June, contributing financially to the household and assisting with the care of Ms Grady’s other children.

Justice Kent recognised there was “underlying and understandable resentment” from Ms Blaze and Ms Darnley towards Ms Grady, who had “changed her mind” about the parenting arrangement.

During the trial Ms Blaze highlighted her concern that Ms Grady might “change her mind again” should she be given custody.

The complicated case has put a spotlight on the dangers of informal adoption arrangements and highlights the ability of the Family Court to negate unofficial agreements.

Whilst a Parenting Plan prepared by legal counsel was entered into by Ms Blaze, Ms Darnley and Ms Grady after the birth, the child’s father Mr Harper was not consulted nor was he aware of the arrangement.

Justice Kent recognised there was no issue regarding Ms Blaze and Ms Darnley’s capacity to provide for the girl, saying the only qualification as to their ability to provide for the toddler concerned “their willingness and capacity to promote the child’s relationship with her parents and biological family.”

Ms Blaze, Ms Darnley and the biological parents will now be subject to a transition period as they are forced to relinquish the care of the young girl they have raised since her birth in 2013.