A four-month-old baby boy suffering stomach pains was given a potentially fatal overdose of the wrong drug by an out-of-hours GP in Weston-super-Mare. In a letter to Karson Bates' parents, seen by BBC News, Dr Stephen EK Boateng said he had been "very tired and exhausted during that shift".

Harmoni, the out of hours company Dr Boateng worked for, has referred him to the General Medical Council.

A spokesperson confirmed Dr Boateng did use the wrong drug and dosage amount.

Dr Boateng inserted a thermometer into Karson's bottom to "relieve gas" and then injected hyoscine hyrdrobromide as a muscle relaxant, instead of hyoscine butylbromide, which should have been injected.

Muscle relaxant

His mother and father, Jodie and Phil, noticed something was wrong when they returned home.

Karson's grandfather, Paul Rodgers, who is a trained fireman with some medical skills, noticed he was in a trance.

"You could see his eyes were fixed and he wasn't aware you were there - he was just sort of blank," he said.

Karson was then taken to Bristol's Royal Children Hospital where doctors said he had been injected with three times the amount he should have been.

Not registered

Harmoni later confirmed that inserting a thermometer was not a normal procedure.

The BBC has not been able to speak directly to Dr Boateng but in the letter to the parents, he confirmed he had worked three consecutive overnight shifts in Portsmouth that week for a different out of hours provider.

Harmoni said they did check with Portsmouth PCT to see if he was registered on their performance list and were told that as he worked for other out of hours providers he must be.

It has since emerged that he was not registered on any Primary Care Trust list and there is not a central registry anywhere in the UK.