One of the conjoined twins born to an 18-year-old British woman has died after an operation to separate them, doctors said yesterday.

London's Great Ormond Street Hospital said week-old Hope Williams had died shortly after the procedure to divide her from her sister Faith.

"Very sadly, after separation, baby Hope's lungs proved too small to support her breathing and she died last night, in the presence of her parents," said surgeon Agostino Pierro.

"They are clearly devastated by the loss of their daughter and we offer them our deepest condolence on their loss."

Laura Williams from Shrewsbury gave birth to the girls last Wednesday at University College Hospital in London.

They were joined from their breast bone to their navel and shared circulatory systems as well as a liver.

Surgeons had brought forward the separation to Tuesday after the health of the babies deteriorated.

Professor Pierro, head of the surgical team that conducted the operation, said there had been a blockage in the twins' joined intestine which could only be resolved by a separation.