Hope Williams, one of the conjoined twins born earlier this week, has died after surgeons performed emergency surgery to separate her from her sister Faith.

Faith’s condition has been described as stable and improving but still critical.

The girls’ parents, 18-year-old Laura Williams and her husband Aled, 28, are said to be “devastated” at the loss of Hope.

The couple refused to have an abortion when doctors told them the twins were conjoined, and last week they described their delight when the girls were born.

Speaking before the birth, Mrs Williams said: “If they’re meant to be in this world and if they’ve come this far, we’ve got to hope they’ll make it the rest of the way.”

Reports after the birth suggested that things were “looking fairly positive” for the twins. However, a blockage in their intestines forced doctors at Great Ormond Street Hospital to separate them earlier than planned.

Sadly, Hope’s lungs were not sufficiently developed to support her breathing, and she died shortly after the operation.

Professor Agostine Pierro, the surgeon who led the operation, said it was “one of the most complex and challenging we have ever faced”.

He said Mr and Mrs Williams were present when their daughter died.

“They are clearly devastated by the loss of their daughter and we offer them our deepest condolences on their loss,” he said.

“Baby Faith is stable after separation, she requires support for her breathing but she is gradually improving.

“However it is early days and complications can occur.”