A police force has defended its decision to arrest the parents of a 15-stone 11-year-old over concerns about his weight.

Norfolk Police confirmed that an un-named 49-year-old man and 44-year-old woman, both from the King's Lynn area, are currently on bail pending further inquiries after concerns were raised about the boy's welfare.

The mother said she and her husband spent 50 minutes in a cell following their arrest.

Their 5ft1in boy has a body mass index of 41.9 - meaning the boy is classed as very overweight - but the woman said the family had been trying to keep him slim.

She added: "The idea they could take away my son scares me so much.

"His weight isn't that much of a big deal.

"I'm chubby and the whole of my husband's side of the family is big. It's genetics - you can be genetically fat."

The woman explained that they encouraged the boy to play active games on his Wii console.

A force spokesman said officers from the child abuse investigation unit worked closely with health and social services to deal with "sensitive issues such as obesity and neglect of a child".

It is understood doctors at the Queen Elizabeth Hospital, King's Lynn, contacted police after the boy, who was already known to social services, was twice brought in for treatment in March.

The mother and father voluntarily attended a police station and were interviewed under caution on suspicion of neglect and child cruelty.

A police spokesman added: "Any action taken by any agency will be subject to a joint strategy between all partner agencies and will always be taken with the welfare of the child and their protection from harm as paramount.

"While it is inappropriate to comment on this case specifically, it is important to stress that intervention at this level is very rare and will only occur where other attempts to protect the child have been unsuccessful."