More hosepipe and sprinkler bans are expected because gardeners are unnecessarily watering lawns and flower beds.

Recent thunderstorms, which have led to flash flooding, have done little to top up reservoirs after the second driest winter since 1904.

The county has also received only 17 per cent of its average rainfall for June, leaving reservoirs low.

Last night, the Environment Agency warned that if water consumption is not reduced water companies in the South of England will have to impose more bans.

The agency is targeting gardeners in its campaign.

It said: "Don't water the lawn. It may turn brown but grass is resilient and it will grow back.

"Garden sprinklers can use as much water in an hour as a family of six uses in a day."

The two main water companies in Sussex, Southern Water, which supplies most of the county, and South East Water, which supplies homes in the Eastbourne area, say unnecessary watering is the problem.

Southern Water introduced a ban in its North Sussex area, covering homes near Crawley, Horsham and north of Chichester at the beginning of the summer.

It has already written to 70 customers suspected of flouting the ban, warning them they could face court action.

It is also writing to customers in the area covered by Weir Wood reservoir, near East Grinstead, reminding them of the ban.

The rain-fed reservoir, which is currently half full, is the main source of water for homes in Crawley and Horsham and cannot be topped up with piped water from areas of the county.

Geoff Loader, communications manager for Southern Water, said: "The thing which could trigger a hosepipe ban in other areas is a hot spell during which gardeners leave hoses and sprinklers running. There has been a good response to our calls to reduce water consumption but garden watering is the key."

Jane Gould, spokeswoman for South East Water, said: "We are at the mercy of the weather. We could be days away from a hosepipe ban if customers use water unnecessarily."

Howard Davidson, regional director for the Environment Agency in the South, said: "We support water companies imposing appropriate restrictions to help safeguard future water supplies and protect the environment."