The national pandemic flu hotline, which will offer the public advice on the spread of the disease and allocate antiviral drugs, should have been ready for operation last October, but wranglings between Whitehall departments prompted lengthy delays.

Internal Whitehall documents obtained by the Observer show the Treasury was expected to sign off the £157m FluLine scheme - a network of public and private call centres, automated voice banks and a website - in June 2008, but did not do so until December.

The hotline is seen in government as vital in the face of a pandemic. But with the launch of the scheme delayed, GPs' surgeries and primary care trusts have been swamped by phone calls since the disease started to spread rapidly.

Instead, the government has been forced to launch an interim swine flu hotline in England this week while the national pandemic flu line will not be in place until the autumn at the earliest. Scotland, Wales and Northern Ireland have instead opted to make their own contingency plans.

The failure has led to questions about whether the interim system will be able to cope with the expected demand for its services. "The whole purpose of the hotline was to ensure primary health care trusts in particular can cope with the enormous pressures and demand they are currently facing," said Norman Lamb, the Lib Dems health spokesman. "This is extremely embarrassing for the government when you consider all the claims that have been made about how we are the best prepared in the world and how we are ahead of the game."

The government pledged as far back as November 2007 that a national flu hotline would be "ready for instant implementation" as soon as the World Health Organisation declared Pandemic Alert Phase 5, which it did on 29 April 2009.

Ministers also said that when the WHO declared a global flu pandemic, as it did on 11 June, the flu line would "expand to provide rapid assessment and where necessary access to antiviral treatment for symptomatic patients". But according to documents released under the Freedom of Information Act to the Lib Dems, the scheme had no chance of being up and running in time because of internal Whitehall arguments. They reveal that the Treasury delayed approving financing for the scheme because it believed the Department of Health (DoH) needed to build public awareness about the hotline ahead of its launch.

The Treasury was also worried about whether the service had the capacity to deal with the number of expected calls and hits to its website when a pandemic broke, jeopardising the country's ability to deal with the disease. According to emails between Whitehall officials and the project's managers, in May 2008 the Treasury signalled it wanted to approve the business case for the new service because "if the flu line does not work properly the whole programme [to combat pandemic flu] would fail".

A status report on the project, compiled between 26 and 30 May 2008, noted: "This extra approval required is likely to increase the information requirements [...] and potentially increase the time taken to authorise the project financials. Any resulting delay could impact the ability to meet the October implementation deadline." A further status report, on 23 June, 2008 expressed the hope the Treasury would sign the project off before parliament's summer recess, "otherwise the preferred supplier is not approved until start of next session - HMT (Her Majesty's Treasury) aware of time pressure".

Over the next six months, emails exchanged between the DoH and the Treasury show the two departments were unable to reach an agreement on how to proceed. As the initial deadline for the scheme's implementation slipped, in October 2008 the Treasury warned: "It strikes us that the timeline for the National Rollout of the awareness campaign (not being until May 2009) is too slow - surely the campaign needs to ensure that there is a high awareness of NHS numbers by the time that flu line is ready?"

On 18 November an official at the DoH emailed a colleague with further Treasury queries about FluLine. "They are concerned about the risk presented by the lack of public awareness of the NHS number, and have the following questions:

i) How far has the awareness work got now? When is it scheduled to be fully rolled out?

ii) What is the strategy for handling contact from the public if a pandemic hits when FluLine is operational but before NHS number awareness has increased?"

By 28 November DoH were chasing the Treasury to sign the project off "but no luck". It was not until 1 December 2008 that the Treasury finally gave approval.

A spokeswoman for the DoH said: "We needed to make sure it was probed and tested sufficiently to ensure value for money." She said the swine flu outbreak earlier this year had prompted the government to focus on providing an interim solution which meant the roll-out of the national hotline has been pushed back from May until this autumn.

Crucial questions

If I go on holiday, what is the risk that I will catch the virus on the flight?

The swine flu virus can be passed from person to person on a flight, but the only people who have so far been affected are those sitting very close to people with symptoms. If a passenger next to you is coughing or sneezing, they should be told to use tissues and then dispose of them. After any similar exposure, you should wash your hands regularly.

Will antiviral drugs such as Tamiflu be offered to people travelling abroad?

The government says it will not provide supplies. It has also warned people not to buy supplies over the internet, as these often turn out to be fake.

When will a swine flu vaccine be available in Britain?

The government has claimed that a vaccine will be ready by the end of August. However, pharmaceutical companies say they still do not know what kind of yields they will get from their production lines and warn that they will need at least four months before they can begin to provide significant supplies to the public.

What are the symptoms of swine flu?

These are similar to those produced by standard flu. A fever - which is a temperature of at least 38C (100.4F) - is the key symptom, combined with complaints that include a cough, sore throat, chills and aching limbs. Some people also suffer nausea and diarrhoea.

If a person catches swine flu now, will this mean he or she will be immune to a potentially more severe mutated version of the virus later in the year?

Doctors say that if you catch swine flu now, it is likely that you will be protected against future infections.

Are children at special risk?

Under-fives are emerging as key swine flu risk groups, according to hospital figures and the age profiles of those who have already died. The chief medical officer, Sir Liam Donaldson, says statistics show that under-fives were three times more likely to need inpatient care than those in other age groups. At least five of the 29 individuals who have died of swine flu in Britain are known to have been young children or babies.