The World Health Organisation has raised concerns about the fast-track production of the swine flu vaccine in Europe, where the treatment is due to be made available at least two months earlier than in the US. Britain is expected to be the first country in Europe to provide the vaccine, with the first of 132 million ordered doses due to be administered next month.

The European Medicines Agency (EMA), the drug regulatory body for the EU, is accelerating the approval process for the vaccine, and countries including Britain, Greece, France and Sweden plan to start using it as soon as it is cleared. The most vulnerable groups, such as pregnant women and young children, will be given priority.

To ensure the vaccine is available as soon as possible, the EMA is allowing companies to bypass large-scale human trials. Amid concerns about bird flu several years ago, the EMA designed a protocol to fast-track the approval of a vaccine. It let companies submit data for a "mock-up" vaccine, using H5N1 avian flu. The idea was to do most of the testing before a pandemic, so that when it hit, the drug companies could insert the pandemic virus into the vaccine.

When the first doses are ready, the EMA will approve them largely based on data from the bird flu vaccine, since both will have the same basic ingredients. The agency will then require regular reporting of the vaccine's effects as it is being administered, monitoring that is normally done beforehand.

The US government is taking a more cautious approach, calling for several thousand volunteers to be injected with the vaccine in tests beginning in August to assess its safety. Officials say the results should be ready in time for the vaccination programme to roll out in October.

But some US officials believe the European approach is the best option. "The consequences of not having a vaccine if this virus gets worse are very high," said Leonard Marcus, a public health expert at Harvard University. "If [regulatory authorities] took all the time that was necessary to make sure there are no side effects, ironically, in the effort to save a few lives, many lives could be lost."

An EMA spokesman said: "Everybody is doing the best they can in a situation which is far from ideal. With the winter flu season approaching, we need to make sure the vaccine is available."

Dr Keiji Fukuda, the WHO's flu chief, warned about the potential dangers of untested vaccines. "There are certain areas where you can make economies, perhaps, but certain areas where you simply do not try to make any economies," he told Associated Press.

The Department of Health said it was "extremely irresponsible" to suggest the UK would use an unsafe vaccine. A spokesman said: "In preparing for a pandemic, appropriate trials to assess safety and the immune responses have been carried out on vaccines very similar to the swine flu vaccine. The vaccines have been shown to have a good safety profile. Over 40,000 doses of the vaccines which the swine flu vaccines are based on have been given without any safety concerns."

Professor Steve Field, chairman of the Royal College of GPs, added: "I'm sure the vaccine programme won't be allowed to commence until adequate safety checks have been carried out."

Earlier this month the head of the WHO, Dr Margaret Chan, said that while a vaccine might be produced next month the clinical trial data to ensure it was safe would not be available for a further two to three months.

Pharmaceutical companies, including GlaxoSmithKline, which is producing the vaccine for Britain, insist they will be able to start shipping the first batches of vaccine before then.

Meanwhile the House of Lords science and technology committee is expected to accuse ministers of failing to keep their promise to set up a flu helpline by April and question the conflicting advice given to the public, in particular to vulnerable groups such as expectant mothers.