The NHS is "ill prepared" for a second wave of swine flu, the Conservatives said.
Thousands of intensive care patients had to be discharged early last year or were transferred to other hospitals in order to get a bed, according to figures obtained by the party.
Shadow health secretary Andrew Lansley said the data showed the system was already at breaking point, although the Government said the NHS could double its intensive care capacity if required and is well-prepared for the pandemic.
NHS figures show there are currently 3,647 adult intensive care beds in England and more for children.
Figures obtained under the Freedom of Information Act by the Tories showed that almost 2,000 people in England had to be discharged early from intensive care last year.
A total of 1,000 patients were transferred to beds in other hospitals while 20,000 patients had their discharge from intensive care delayed owing to shortages of beds in wards to be transferred to.
On average, hospitals had all their intensive care beds full for almost a third of the year in 2008, the Tory data showed.
Hospitals also had at least one of their intensive care beds closed due to a lack of staff on 25 days in 2008.
Research has shown that many more intensive care (also called critical care) beds are likely to be needed in the winter when an expected second wave of swine flu hits the UK.
The UK has fewer intensive care beds per 100,000 people than any other country in Western Europe or the US.
