A Spanish woman whose identity was swapped at birth with another baby born hours earlier is suing the regional health department for more than three million euros ($A4.8 million).
The health department in the northern region of La Rioja said in a statement on Tuesday that an internal investigation found an undetermined "one-off human error" was to blame and added it would respect any judicial proceedings.
"We are not aware of any other cases," it said, adding that current systems in place would prevent any similar mix-up from happening again.
The 19-year-old woman, who prefers to remain anonymous, was born in 2002 in the San Millan de Logrono hospital in La Rioja some five hours after another baby girl.
"In the case of my client, she was born later but was given to the mother who gave birth to the first child," Jose Saez Morga, the lawyer, told the TVR television network.
"This is negligence so gross that it speaks for itself."
He said he had filed a claim on behalf of his client against La Rioja's health department for immeasurable emotional harm caused by the error.
The lawyer could not be reached for further comment.
According to the larioja.com news site, the girl grew up in a dysfunctional family and was mostly raised by her grandmother.
The error came to light in 2017 after her alleged father demanded a paternity test during a child support dispute, which confirmed she was unrelated to the family she grew up with.