Anyone infected with swine flu could stay off work for 14 days without a doctor's note, under government plans to deal with the pandemic.

Employees can currently be off for seven days, including weekends and bank holidays, without needing a sick note from their GP.

A spokesman for the Department for Work and Pensions said: "The government is rightly considering possible measures to minimise the risk of further spread of swine-flu and protect public health.

"We don't want people to feel obliged to leave the home or return to work when they are still unwell or put an unnecessary burden on GPs in a pandemic. Contingency plans therefore include the possibility of extending self-certification to 14 days for a limited period."

He said the measures would "only be implemented if absolutely needed", and the decision would be taken by the government's civil contingencies committee.

Professor Sayeed Khan, chief medical adviser at the manufacturers' body EEF, said: "We are going to have GPs – quite rightly – dealing with more serious cases. The advice is not to visit your GP if you get swine flu.

"Being realistic, there will be some people who think 'I've got a bit of a cold' or 'I'm not that bad' and will stay off work. There's nothing you can do to fix that. Employers can rely on the good morals of their employees and say 'don't abuse it'. They can say they will take tough measures against anyone found abusing it, but that's about all they can do."

The move follows the government's chief medical officer announcement yesterday that the number of deaths from swine flu had risen to 14, with the infection reaching epidemic levels in the worst-hit parts of the country, such as London and the west Midlands.

The Health Protection Agency revealed a snapshot of the numbers going to hospital in a serious condition. Yesterday, 335 people were being treated, 43 of whom were in critical care. Sixty of those in hospital were under five years old, 47 were aged five to 15, 189 were 16-64 and only 39 were over 65.

Exact figures for the numbers of people diagnosed as having swine flu are no longer being given, because of the large numbers infected. Sir Liam Donaldson, the chief medical officer, said about 27,000 people had consulted a GP with symptoms in the last week, but the HPA said its sampling showed that only about 28% – 8,000 or so people – of those had a flu-like illness.

The government's national framework for dealing with a flu pandemic estimates that up to 50% of the workforce may require time off at some stage, "with individuals absent for a period of seven to 10 working days". Staff may also need time off to care for family members with swine flu and some may suffer "other psychosocial impacts, fear of infection and/or practical difficulties in getting to work," the plan says.

Small firms, with five to 15 staff, or small teams within a larger organisation are likely to suffer more, with a higher proportion of staff absence. This could mean up to 35% of their workforce off over a two or three-week period at the peak of a pandemic.

Neil Carberry, head of employment policy at the CBI, said it was likely that temporary changes to sick leave policy would have to be taken.

"Employers need to be thinking through their business resilience plans in the face of threat of pandemic. The impact of a pandemic outbreak is going to be the significant threat to employers, not necessarily some of the temporary measures," he said.

The plans were revealed as it emerged that some senior NHS managers had criticised the government's pandemic flu strategy as muddled and contradictory. Health trust chiefs also claimed that the introduction of vouchers for Tamiflu would hamper the rapid distribution of antiviral drugs, according to the Times.

A memo obtained by the paper sent by an NHS trust executive responsible for emergency planning to other senior NHS staff described some measures to distribute drugs and relieve pressure on hospitals and GPs as "a complete waste of time".

Ian Dalton, the government's national director of flu resilience, said the NHS was "coping very well with the challenges" posed by swine flu.

"However, now that we have moved into the treatment phase, further clear guidance has been provided to the NHS on its roles and responsibilities," he said. "Although this is being centrally led, the local NHS clearly must ensure that these plans are implemented in a way that meets local needs."

The UK's swine flu case total is the third highest in the world after Mexico, where the bug was first identified, and the US. There are 9,718 confirmed cases of swine flu in the UK. Mexico has 10,262 cases of the disease, with 33,902 in the US.