The UK Influenza Pandemic Contingency Plan does not consider the impact of a pandemic on critical care services. We modelled the demand for critical care beds in England with software developed by the Centers for Disease Control (Flusurge 1.0), using a range of attack rates and pandemic durations. Using inputs that have been employed in UK Department of Health scenarios (25% attack rate and 8-week pandemic duration) resulted in a demand for ventilatory support that exceeded 200% of present capacity. Demand remained unsustainably high even when more favourable scenarios were considered. Current critical care bed capacity in England would be unable to cope with the increased demand provided by an influenza pandemic. Appropriate contingency planning is essential.