A girl of seven was sent home from hospital with a broken arm after medics X-rayed the wrong one.

Kerry Pullinger spent 12 hours in agony because of the blunder.

Doctors at the Royal Sussex County Hospital in Brighton even advised her to exercise the arm, saying it would help the bruising to heal.

Bosses last night apologised for the mistake and promised to carry out a full investigation.

But the schoolgirl's mother, Karen, said: "It's just disgraceful."

Kerry broke her left arm just below the shoulder when she fell off a swing in her back garden. She was taken to casualty and then the X-ray department. Miss Pullinger was looking after her three other children when the picture was taken.

She said: "I left the hospital staff to get on with it. You expect them to know what they are doing."

Kerry's injured arm was not put in a sling and Miss Pullinger was told to encourage her daughter to keep moving it so it wouldn't stiffen up.

Miss Pullinger said: "Later that evening Kerry was still in a lot of pain and wouldn't stop crying.

"At one point I was starting to get angry with her because I thought she was putting it on.

"The hospital had told us the arm wasn't broken so we obviously believed them."

When Kerry's pain continued Miss Pullinger contacted the hospital but staff said there was no way they could have made a mistake and insisted there was no need for her to go back in.

The next morning Kerry was still in agony. Miss Pullinger marched her back to casualty and demanded another X-ray. The image showed the arm was clearly broken.

Miss Pullinger said: "It's just disgraceful. Kerry is only seven but has had to go through so much unnecessary pain.

"And who knows what extra damage has been done because it wasn't treated properly straight away?"

Kerry's arm will take at least three weeks to mend and meanwhile she has had to take a week off before going back to join her classmates at St John the Baptist Primary School.

Miss Pullinger said: "No wonder she was so upset.

"I will certainly be taking this further.

"I don't want another child to go through what Kerry has."

A hospital spokesman admitted x-raying the wrong arm, saying: "This is something we take extremely seriously. An investigation is now under way to understand how this happened and to make sure it doesn't happen again.

"We are obviously very sorry that it happened and apologise to the family.

"We will welcome the family getting in contact with us and will keep them informed about the results of the investigation."

The blunder comes just days after new mother Nathalie Brooks was given the wrong baby to breast feed following a mix-up at the maternity ward at Eastbourne District General Hospital.