The Mexican authorities have been accused by doctors of trying to cover up the scale of the swine flu outbreak.

Dr Antonio Chavez, a specialist in respiratory diseases at the Mexico National Institute of Health, said there was panic as medical staff in Mexico City struggled to deal with the problem.

Another doctor claimed that in the early stages, staff were asked not to place the cause of death on death certificates.

More than 100 deaths in Mexico have been connected to swine flu, but only 18 cases have been definitively linked to the virus through laboratory testing. A further 1600 people have complained of flu-like symptoms since the authorities publicised their concern about the virus on April 23.