Experts warn there are too few NHS critical care beds in England to cope with an outbreak of avian flu.
Around 37,548 people might need to be hospitalised
Scientists say it is only a matter of time before bird flu becomes readily transmissible between humans, which could cause a pandemic.
For their work in Anaesthesia, the Intensive Care Society team created a model to estimate the impact of an outbreak on critical care services.
The government said it was aware of the threat and was working to address it.
The study authors estimate a doubling to tripling of current capacity is needed.
Their work assumes that an epidemic would last eight weeks and would affect one in four people in England.
With this level of infection, they estimate there would be 37,548 people hospitalised for avian flu, occupying a third of all available acute hospital beds in the country.
These patients would be very sick and need access to expert care and ventilators to help their breathing.
This demand would represent 208% of the current bed capacity, they say, which would completely overwhelm hospitals.
Dr Bruce Taylor, one of the study's authors and consultant in intensive care and anaesthesia at Portsmouth Hospitals NHS Trust, said: "It would overwhelm the system."
He warned that staff would also be struck down with flu as well as patients, which would compound the problem.
But he said antiviral drugs, which the UK has been stockpiling, would help.
The government has ordered around 14.6 million courses of the drug Tamiflu - enough to treat around a quarter of the UK's population.
The drug reduces the severity of flu symptoms and can also mean the length of illness is shortened.
Chief Medical Officer, Sir Liam Donaldson said: "Expert opinion suggests that these drugs will help to reduce the health impact of a pandemic and could cut the demand for acute hospital beds by as much as 50%."
He said the Department of Health was aware of the issue and that this latest work, although it only applied to England, would be helpful for planning a flu response across the UK.
He said the department was working with intensive care doctors to determine how to address the issues raised.
"We are also asking the NHS to develop local plans setting out how they will respond to a flu pandemic. These plans will include how best to use existing resources to cope with an increase in the number of critical care patients.
"We take the possibility of a flu pandemic very seriously. The World Health Organisation has said that the UK is at the forefront of preparations internationally for a pandemic influenza."
The UK Health Protection Agency estimates that around a quarter of the population could be affected by avian flu in the future, with possibly 50,000 deaths in England and Wales alone.