People with swine flu could stay off work for 14 days without a doctor's note under Government plans to deal with the pandemic.
Currently, employees can be off for seven days, including weekends and bank holidays, without needing a sick note from their GP.
But the Government could allow swine flu victims to take two weeks off before they are required to prove they are ill.
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."
The spokesman said the measures would "only be implemented if absolutely needed" and the decision would be taken by the Government's Civil Contingencies Committee.
Critics said the system could be open to abuse, with some employees staying home when they are fine to go to work.
Professor Sayeed Khan, chief medical adviser at manufacturers' body the 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."
Fourteen people in the UK are now thought to have died after contracting swine flu and hundreds of thousands more are suffering with the virus.
Chief Medical Officer Sir Liam Donaldson said yesterday there are 43 people in critical care in England with swine flu, and another 292 in hospital.
The Government's national framework for dealing with a flu pandemic says 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," it says.
Small firms, with five to 15 staff, or small teams within a larger organisation are likely to suffer higher percentages of staff absence.
This could mean up to 35 per cent of their workforce off over a two or three-week period at the peak of a pandemic.