Almost nine out of 10 GPs fear people with serious conditions such as tonsillitis, bronchitis and meningitis could be wrongly diagnosed as having swine flu by the new telephone helpline.

In a survey of 251 family doctors, 87% said that diagnosing swine flu over the phone did mean that other diseases may be missed. The findings raise questions about the National Pandemic Flu Service, which handles half of all calls with an operator, and the other half via its website.

In comments to GP newspaper, which ran today's poll, one GP said: "Saw a case today of measles which was diagnosed over the phone as swine flu." Another said: "Patients are making up symptoms in order to get Tamiflu and for example meningitis or tonsillitis or bronchitis/pneumonia may be missed."

Another GP said he had seen two cases of tonsillitis and a knee infection who were prescribed Tamiflu over the phone.

Professor Steve Field, chairman of the Royal College of GPs, said: "The new helpline is not a substitute for GPs diagnosing a patient's illness; it's only there to decide if someone should get Tamiflu. The symptoms of swine flu are very similar to some other conditions."

It emerged yesterday that a 13-year-old boy in Bristol with a kidney infection ended up in hospital for six days after being wrongly diagnosed with flu over the phone by an out of hours GP service.