An inquest is likely to be held into her death at the age of 35.

Lena was admitted to the 1,800-bed University Hospital of Wales in Cardiff last month for the treatment.

The child star had an eating disorder by the age of 13

She had the operation - in itself not thought to be dangerous - two weeks ago but developed a blood infection which caused heart failure.

Her father Victor, aged 60, was at her bedside when she died.

Hospital spokesman Bob Burrows said: "Everyone at the hospital is upset that someone so young has died.

"She had made friends with many of our medical staff and had become very popular in the time she was with us."

Mr Burrows declined to discuss the brain operation carried out on Lena.

However, it is understood to have been a leucotomy, an operation that involves cutting into the brain and is considered to be low risk.

The operation was developed in the 1930s, when the medical establishment embraced it enthusiatiscally.

It remained popular until the late 1950s when, with the introduction of effective drugs, the operation became a rarely-performed procedure.

Doctors wishing to perform a leucotomy now must first get a second opinion and then permission from the Mental Health Act Commission.

Mr Burrows said: "Miss Zavaroni came to Cardiff because we are one of the few centres that carry out this operation.

"The singer's death will be reported to Cardiff Coroner Dr Lawrence Addicott because she died following elective surgery."

Talent show

Lena was born on the Isle of Bute in Scotland and shot to stardom at the age of 10 on Hughie Green's talent show in the 1970s.

But she developed an eating order by the time she was 13 and at one time her weight went down to 3 stone 12lbs.

She was so ill that she begged doctors to remove part of her brain that she believed was controlling her anorexia.

Before going in to hospital Lena was living in a council flat and surviving on £48.80 state handouts and getting help from the showbusiness charity The Water Rats.