Essex social services obtained a High Court order against the woman that allowed her to be forcibly sedated and her child to be taken from her womb.
The council said it was acting in the best interests of the woman, an Italian who was in Britain on a work trip, because she had suffered a mental breakdown.
The baby girl, now 15 months old, is still in the care of social services, who are refusing to give her back to the mother, even though she claims to have made a full recovery.
The case has developed into an international legal row, with lawyers for the woman describing it as “unprecedented”.
They claim that even if the council had been acting in the woman’s best interests, officials should have consulted her family beforehand and also involved Italian social services, who would be better-placed to look after the child.
Brendan Fleming, the woman’s British lawyer, told The Sunday Telegraph: “I have never heard of anything like this in all my 40 years in the job.
“I can understand if someone is very ill that they may not be able to consent to a medical procedure, but a forced caesarean is unprecedented.
“If there were concerns about the care of this child by an Italian mother, then the better plan would have been for the authorities here to have notified social services in Italy and for the child to have been taken back there.”
The case, reported by Christopher Booker in his column in The Sunday Telegraph, raises fresh questions about the extent of social workers’ powers.
It will be raised in Parliament this week by John Hemming, a Liberal Democrat MP. He chairs the Public Family Law Reform Coordinating Campaign, which wants reform and greater openness in court proceedings involving family matters.
He said: “I have seen a number of cases of abuses of people’s rights in the family courts, but this has to be one of the more extreme.
“It involves the Court of Protection authorising a caesarean section without the person concerned being made aware of what was proposed. I worry about the way these decisions about a person’s mental capacity are being taken without any apparent concern as to the effect on the individual being affected.”
The woman, who cannot be named for legal reasons, is an Italian national who come to Britain in July last year to attend a training course with an airline at Stansted Airport in Essex.
She suffered a panic attack, which her relations believe was due to her failure to take regular medication for an existing bipolar condition.
She called the police, who became concerned for her well-being and took her to a hospital, which she then realised was a psychiatric facility.
She has told her lawyers that when she said she wanted to return to her hotel, she was restrained and sectioned under the Mental Health Act.
Meanwhile, Essex social services obtained a High Court order in August 2012 for the birth “to be enforced by way of caesarean section”, according to legal documents seen by this newspaper.
The woman, who says she was kept in the dark about the proceedings, says that after five weeks in the ward she was forcibly sedated. When she woke up she was told that the child had been delivered by C-section and taken into care.
In February, the mother, who had gone back to Italy, returned to Britain to request the return of her daughter at a hearing at Chelmsford Crown Court.
Her lawyers say that she had since resumed taking her medication, and that the judge formed a favourable opinion of her. But he ruled that the child should be placed for adoption because of the risk that she might suffer a relapse.
The cause has also been raised before a judge in the High Court in Rome, which has questioned why British care proceedings had been applied to the child of an Italian citizen “habitually resident” in Italy. The Italian judge accepted, though, that the British courts had jurisdiction over the woman, who was deemed to have had no “capacity” to instruct lawyers.
Lawyers for the woman are demanding to know why Essex social services appear not have contacted next of kin in Italy to consult them on the case.
They are also upset that social workers insisted on placing the child in care in Britain, when there had been an offer from a family friend in America to look after her.
An expert on social care proceedings, who asked not to be named because she was not fully acquainted with the details of the case, described it as “highly unusual”.
She said the council would first have to find “that she was basically unfit to make any decision herself” and then shown there was an acute risk to the mother if a natural birth was attempted.
An Essex county council spokesman said the local authority would not comment on ongoing cases involving vulnerable people and children.