The degenerative bone condition - caused by poor diet - has virtually disappeared in the UK in the past 60 years.

The youngster from Glasgow is being treated at the city's Yorkhill children's hospital.

She is thought to have suffered a number of fractures, caused by a lack of vitamin D.

Doctors are under pressure to report her parents to social workers for neglecting the child by denying her meat and dairy from birth.

Vitamin D is needed to absorb calcium and is found in liver, oily fish and dairy produce.

In most cases, vegan parents will give their children vitamin and mineral supplements to avoid putting their child at risk.

There are concerns that the child's parents put their own beliefs before the girl's welfare.

The couple are well-known figures in the vegan community.

Yorkhill's Dr Faisal Ahmed insisted it was important to highlight the dangers of a vegan diet to children.

He said: "Something like this needs publicity. But we shouldn't name and shame. Mum feels guilty about the whole thing and feels bad about it."

Greater Glasgow and Clyde NHS board refused to comment on the case while Glasgow City Council said the matter has not been reported to social workers.

Professor Tom Sanders, head of nutrition at King's College, London, warned: "Some vegan hard-liners think we're still monkeys and can live on fruit and nuts."