Look out of the window and the problem might not be obvious, but Britain faces a drought. The Environment Agency warned yesterday that serious water shortages were on the way next year unless one-fifth more rain than usual falls in the next four months.

People were advised to begin replacing worn tap washers, using less water in kettles and saucepans, choosing half-loads for washing machines and dishwashers, and washing vegetables in a bowl rather than under a tap.

Seven water companies have taking measures to ensure supplies to customers because the recent wet weather has not replenished rivers and reservoirs, which stand at about half the level they would normally be at this time of year. Rainfall has been about two-thirds of the long-term average since January.

A spokesman for Water UK, which represents the private water utilities in England and Wales, and the water companies in Scotland and Northern Ireland, said: "There weren't any hosepipe bans this year, but potentially if it doesn't rain enough we would be looking at restrictions in the New Year."

Britons use 15 billion litres of water per day, but water companies have had to share heavily among each other this year, with the hottest day on record adding to demand.

Barbara Young, the agency's chief executive, said: "Although supplies are secure for the coming winter, unless we receive higher than average rainfall between now and March we could be faced with water restrictions and serious water shortages in 2004."

The period since February has been the second-driest in England and Wales since 1921, and the driest since 1959.

The worst hit region is the South-east, where over the past three months some parts have seen as little as 30 per cent of the average rainfall, leaving rivers flowing at only 20 per cent of normal for the time of year.

Thames Water has been given two "drought permits" which let it take more water than usual from the Thames and from groundwater sources.

Ms Young said: "If the entire adult population of England and Wales turned the tap off while brushing their teeth, it could save up to 180 million litres per day - that's enough to supply nearly 500,000 households on a daily basis."