The baby was born to the 18-year-old, who has just left local authority care, in hospital in the early hours of Wednesday morning.

Ian Wise, appearing at the High Court for the mother on Wednesday, said the child was born healthy just after 2am and taken from his mother about 4am without her consent.

He was removed after staff at the hospital were shown a "birth plan" prepared by social workers. The plan said the mother, who had a troubled childhood and suffers from mental health problems, was to be separated from the child, and no contact allowed without supervision by social workers.

Mr Justice Munby said that "on the face of it" social services officials in Nottinghamshire had acted unlawfully because they had not obtained a court order.

He said removal of a child can only be lawful if a police constable is taking action to protect a child, or there is a court order in place. He said no baby can be removed simply "as the result of a decision taken by officials in some room".

The judge ordered that the baby be immediately returned to his mother, who can only be referred to as "G".

Later, the mother's solicitor, Stuart Luke, from the firm Bhatia Best, said: "Mother and child were reunited 46 minutes after Mr Justice Munby's order at 1209."

He said she planned to "vigorously contest" an application by the local authority social services for an interim care order.

Mr Luke added that G is also launching a claim for damages against the social services officials "arising out of the unfortunate removal of her child without lawful authority shortly after his birth".