They were unaware of each other's existence for nearly 30 years, until their uncanny likeness caused a misunderstanding at a clothes shop that led to their reunion.

Now one of the identical twins - separated at birth 35 years ago after a mix-up at the hospital where they were born - is suing the Spanish health authority for a mistake that led to her growing up in the wrong family.

The woman is seeking €3 million (£2.4 million) in damages for the error, which came to light after she was spotted in a shopping centre by a friend of her twin sister. “In just one day, my world fell apart,” she said of the chance reunion. “I wish it had never happened.”

In an attempt to shield them from the intense media interest that their case has generated, her lawyer, Sebastián Socorro, has not revealed the women's identities. The case is further complicated by the existence of a third victim: the baby who was inadvertently switched with one of the twins when they were born.

The reunion occurred in 2001 after one of the sisters walked into a shop in the Canary Islands. The assistant was taken aback by the unfriendly manner of the woman who she thought was her friend, and offended that she did not even say hello.

When the shop assistant called her friend to upbraid her about the snub, she was assured that the friend had not been at the shopping centre. A few days later, when the other woman came into the shop again, the assistant approached her and began to ask questions. “The similarity was crushing,” the shop assistant said. “They were like two drops of water.”

Astounded by their likeness, she arranged a meeting between the two sisters. Standing in front of each other, as if facing a mirror, the siblings began to compare notes. One of them said she had a twin sister but that they did not look alike.

They had been born at the same hospital, it emerged, but apparently three days apart. In fact, the lawyer explained, it was the other girl who had been born three days after the twins. Their documentation had also been switched in error.

The twins decided that the only way to confirm what had happened would be to take a DNA test. But the twin who had grown up with the wrong family got cold feet, the lawyer said.Three years later, she relented and took the test, which concluded that the two were genetically identical.

Mr Socorro said that the similarity between the twins was striking. “They walk the same, they talk the same, they have the same look and the same tone of voice,” he said.

They lodged a complaint with the Canary Islands health authorities but, their lawyer said, they “were met with complete apathy from the very first”. Now his client was suing the health authority for “moral damages” and malpractice. “She has received years of psychological treatment,” Mr Socorro said.The Canary Islands government did not immediately respond to calls for comment.

The identity of the third woman in the case remains a mystery: it has yet to be ascertained whether those who brought up the twin with whom she was swapped at birth are in fact the third woman's parents.

Mixed doubles

— Holly and Douglas Funk discarded their hopes of adopting twins when they found Mia in a Chinese orphanage in 2006. Back in Chicago they joined an internet chatroom and met Carlos Ramirez, who had also adopted a child from Yangzhou and named her Mia. Their stories matched, and DNA tests revealed that the two Mias were twins

— In 2007, 35 years after their adoptions, Elyse Schein and Paula Bernstein discovered each other in New York and found out that they had been separated purposefully as part of a study in the relative influences of nature and nurture. They had both studied film at university and were writers

— In 2001 Wendy Brooks found her twin brother, John, on the internet after 62 years apart. The twins, aged six weeks, had been left in a cardboard box on a doorstep in Cheltenham, Gloucestershire, at the outbreak of the Second World War, and separated soon after

— A chance meeting in 2003 brought together Adriana Rabi and Rabi Scott, neither knowing that she had a twin. They had had the same nightmares as small children, and now dance together for a DJ outfit

Source: Times archives

Times Recommends

• No apology for Germany’s own Nazi victims
• Intricate web of fear and hope tying down deal
• Victims remembered a year after Mumbai attacks