The drug did not reduce the duration of symptoms, how long the children had off school or if the illness reoccurred.

Researchers writing in the British Medical Journal said doctors should prescribe penicillin "prudently".

They add that the drug should only be given to children with an acute sore throat if they are severely ill or at high risk of serious complications.

This very much fits in with current thinking in general practice Dr Mayur Lakhani, Royal College of GPs

Dutch researchers studied 156 children aged four to 15 who visited their doctor with a severe sore throat.

They were either given penicillin for seven days, for three days followed a dummy pill for four days, or for seven days.

It was found that penicillin did not reduce the duration of symptoms, nor did it affect school attendance or recurrences of sore throat.

But the researchers found penicillin could reduce the development of complications, such as throat inflammation (quinsy) or scarlet fever.

They said there was still time to treat a child with penicillin if a complication was diagnosed.

'Engaging patients'

Writing in the BMJ, researchers from the University Medical Centre, Utrecht in the Netherlands led by Dr Sjoerd Zwart, said: "We advocate prudent prescription behaviour with respect to penicillin.

"GPs are recommended to treat children having an acute sore throat only when they are severely ill or at high risk."

Dr Mayur Lakhani, a spokesman for the Royal College of GPs, told BBC News Online: "This very much fits in with current thinking in general practice.

"There has been a decrease in the use of antibiotics in recent years.

"This study is helpful because it confirms what we believed to be the case."

He said patients were becoming more aware that antibiotics such as penicillin would not always relieve their symptoms.