Lords report will criticise the Government's handling of crisis and blame it for failing to quell the panic that has gripped the nation

Drug addicts could be among those given priority for vaccines against the virus, the official in charge of the Government's response to the swine flu pandemic has suggested.

Professor Lindsey Davies, director of Pandemic Influenza Preparedness, told a parliamentary committee that people with long-term maintenance conditions, such as those receiving methadone treatment, could be included in the "vulnerable" groups that the NHS will target first.

The suggestion, which is likely to cause controversy, was made to the Lords science and technology committee, which will publish a damning report this week into the Government's handling of swine flu.

With more than 100,000 people reported to have caught swine flu last week, the Government said last night that its new helpline and website were working well. More than 58,000 assessments were made by the National Pandemic Flu Service, 89 per cent of which were completed on the internet, and 5,584 courses of Tamiflu were collected, the Department of Health said.

Doctors in Stockholm, Sweden, continued to treat a pregnant swine flu victim, Sharon Pentleton, 26, who is described as "stable, but still critical". She was flown from Crosshouse Hospital in Kilmarnock, Scotland, to Karolinska University Hospital for specialist care involving extracorporeal membrane oxygenation (which involves pumping oxygen into her blood) after she suffered a rare and severe reaction to the virus and developed adult respiratory distress. The Foreign Office is still assisting at least 160 British nationals in quarantine because of swine flu in China, Singapore, India, Egypt.

The IoS has learnt that the Lords committee will criticise the belated introduction of the national swine flu helpline and website, swamped by anxious sufferers and "worried well" after they were launched last week. The peers will also demand to know why "whole-system testing" – from the moment a suspected flu sufferer contacts the NHS to their treatment and recovery – was not carried out until the swine flu virus was already in Britain.

The committee began a follow-up inquiry into pandemic influenza last year, after its 2005 report on the avian flu outbreak, and held an evidence session in March on the Government's preparations for the possibility of a major flu outbreak, just weeks before swine flu emerged.

Professor Davies was asked by the Tory former cabinet minister Lord Crickhowell about measures put in place for those with "long-term maintenance conditions", including those on kidney dialysis and drug addicts, in the event of a pandemic. He replied: "We are encouraging, through the guidance, every local NHS organisation to look carefully at these vulnerable people – and all those with long-term conditions come into that. The Cabinet Office has recently produced guidance on vulnerable people in emergencies generally, but we are working on something more specific for people with health issues."

The term "vulnerable" is crucial because the NHS is preparing a list of those who would be given priority for vaccines. This is expected to include the young, the elderly and diabetics, but it is the first suggestion that people on methadone would also be towards the front of the queue.

"We can't confirm that people on methadone treatment are classed as people with long-term conditions," the Department of Health said yesterday. "Professor Davies was talking generally about people who have immune suppressive systems – the actual priority groups are yet to be decided."

A report by the committee in 2005 on the threat of a flu pandemic recommended that "whole system" or "end-to-end" testing be carried out – which the committee will say was ignored by ministers and officials.

Huge gaps emerged in the distribution network for Tamiflu on Friday with claims that there were not enough locations to get the drug. In one example, sufferers in Leeds were told to visit chemists up to 70 miles away.