Children should not be given the anti-viral drug Tamiflu to combat swine flu, Oxford University researchers have said.

They urged the Department of Health to urgently rethink its policy on giving the drugs to youngsters affected by the current flu pandemic.

The study, published in the British Medical Journal (BMJ), warned that Tamiflu can cause vomiting in some children, which can lead to dehydration and the need for hospital treatment.

Some 300,000 people in England, including children and adults, have received courses of Tamiflu through the Government's National Pandemic Flu Service for England.

The researchers said children should not be given the drug if they have a mild form of the illness although they urged parents and GPs to remain vigilant for signs of complications.

Parents of children with a compromised immune system or a condition like cystic fibrosis should discuss the harms and benefits with their GP, they said.

But overall, the researchers said, children who were otherwise healthy could suffer more harm than benefit from taking Tamiflu or another anti-viral, Relenza.

They found the drugs had little or no effect on asthma flare-ups, ear infections or the likelihood of a youngster needing antibiotics. The researchers also found that using anti-virals preventatively had little effect - reducing transmission of flu by 8%. This means 13 children would have to be treated to prevent one additional case of the flu.

However, anti-virals could reduce symptoms by between half a day and one day.

Dr Carl Heneghan, a GP and clinical lecturer at Oxford University, said the current policy of giving Tamiflu for mild illness was an "inappropriate strategy". He added: "The downside of the harms outweigh the one-day reduction in symptomatic benefits."