The website for the new national pandemic flu service in England crashed on launch today as the government announced that the number of new swine flu cases had doubled in a week and that 840 people were seriously ill in hospital.

People trying to access the site, which was officially launched at 3pm, were told it is "currently very busy and cannot deal with your request at this time".

Viewers were told to try again "in a little time". The website crash is potentially extremely embarrassing for the government, which promised it would be launched only when it had been proved capable of coping with the expected traffic.

The service is designed to take pressure off GPs, help patients diagnose themselves and gain access to antiviral drugs without formal prescriptions, although callers are issued with identification numbers.

Liberal Democrats said the website crash raised serious questions about the robustness of the system. "The government claims the reason for the delay in setting up this service was because they needed to thoroughly test it to ensure this wouldn't happen," said health spokesman Norman Lamb. " It is absolutely vital that the public has access to a reliable source of information on swine flu to provide reassurance and take the pressure of GP surgeries."

Meanwhile the government's chief medical officer said in the UK as a whole, 840 people were seriously ill in hospital with swine flu and 100,000 new cases had been recorded in the last week. The number of people in hospital included 63 in intensive care.

The figures were given by Sir Liam Donaldson during a press conference at the Department of Health, to provide a weekly update on the progress of the disease throughout Britain.

The number of deaths associated with the swine flu outbreak has risen to 30. Last week the government announced there had been 29 deaths in total and 55,000 new cases in the previous week.

The National Flu Pandemic Service for England, which started today, will be capable of answering more than a million calls a week, it was confirmed today. It will be staffed by more than 1,500 people, with the option of recruiting 500 more.

They will, it is hoped, be capable of answering more than 200,000 calls a day. There will be an alternative internet service where people answer a questionnaire to receive a diagnosis of swine flu and are given a unique code authorising the release of antiviral drugs.

The details emerged as scientists suggested the outbreak may have peaked for in Scotland, implying that the surge in cases in England could also subside within weeks. One of the planning scenarios used by the DoH assumes the figures will fall during the summer, when schools are on holiday, and then surge again once term starts in the autumn.

People whose holiday plans have been wrecked by swine flu, because of a diagnosis through the pandemic flu service in England, will have to keep the label from the anti-flu drugs they collect if they are to claim from insurers, the Association of British Insurers (ABI) said last night.

Insurers usually require a medical certificate from a GP or other medically qualified staff, and had raised concerns that people would be given diagnoses and access to drugs by people who were not medically qualified.

Nick Starling, the ABI's director of general insurance and health, said it had been told by the government the service would authorise an anti-flu prescription only to those genuinely displaying signs of flu.

"On that basis, travel insurers will accept an individual's unique ID number generated by the national flu service together with the label on their anti-flu drugs which states their name and date of issue, as proof of diagnosis to validate a travel insurance cancellation claim."

The archbishops of Canterbury and York have recommended the suspension of the sharing of the chalice at communion as the spread of swine flu continues, it was announced today.

The archbishops have written to bishops in the Church of England setting out the new measures following DoH advice not to share "common vessels" for food or drink.

The letter said it aimed to offer guidance at a national level about how church worship could "best take into account the interests of public health during the current phase of the swine flu pandemic".

Some bishops have already taken the step to limit the spread of the virus.