In some parts of the southeast, reservoirs are at less than half their capacity at a time when they should be at or near full as the country emerges from the winter.

"We are in a serious situation now, where both the environment and our water supplies are at risk," agency chief Barbara Young said. "Groundwater levels in some areas are the lowest on record."

She called for water companies to bring in hosepipe bans by April at the latest and for non-essential water use such as washing cars and windows to be outlawed.

"If water companies delay introducing hosepipe bans now, extreme steps to manage water supplies over summer may be needed, such as standpipes and rota cuts," she added.

Rainfall over the winter months has been the lowest since the major drought of 1920/21, and Young warned that even if it returned to normal over coming months there would still be serious problems in some areas.

The country has suffered seven major droughts in the last century, with the most recent taking place 10 years ago

Britons use on average 150 litres of water a day, and Young said if everyone managed to cut down consumption by just four litres a day -- say by turning taps off while brushing their teeth -- it would be enough to supply 600,000 homes.