Londoners will face their first hosepipe ban in 15 years under new water restrictions imposed next month.

Thames Water will prohibit the use of hosepipes and sprinklers in the garden or for washing cars from April 3.

The decision follows 15 months of below average rainfall across the South-East. Last year was the third driest since records began just over a century ago.

But Darren Johnson, chair of the London Assembly's environment committee, said: "A hosepipe ban will not solve the problem - merely defer it."

Thames Water's leakage record is the worst in the country. In 2004 the capital lost almost 1,000 million litres a day, or 17 Olympic sized swimming pools an hour, through leaks.

Unless Thames Water took "real action" to cut water loss through leakage, the ban will be the "first step on the slippery slope that ends with water rationing", Mr Johnson said.

Jeremy Pelczer, chief executive of Thames Water, said: "We are reluctant to restrict the amount of water our customers use, but the situation is serious.

"By taking this step now, we will lessen the likelihood of more stringent restrictions later but much still depends on how much rainfall we receive in the coming weeks."

If the drought continues, the company "may have to go further" and restrict other non-essential uses of water, Mr Pelczer added.

"We have now had two dry winters in a row. Winter is a vital time, when substantial rainfall normally soaks down through the soil to top up the underground water sources that feed rivers and boreholes.

"This doesn't happen in the spring and summer, because a lot of the water is taken up by evaporation and plant growth."

Thames Water said it spends more than £500,000 a day to reduce leakage.

It has replaced 250 miles of pipework in London, where a third of the pipes are over 150 years old. More than 1,000 people are renewing mains in 20 locations across the capital.

Mr Pelzcer said customers should think twice about how they use water. "It's not just in the garden that people can help make a difference. There are lots of things they can do in and around the home, without making big changes to their lifestyle."

The Environment Agency, which recently urged water companies to preserve supplies, welcomed the announcement.

David Willis, the agency's environment manager for the Thames region, said Thames Water was "acting responsibly" by banning hosepipes now.

"Given the current status of our water resources, water companies must take action to reduce risks to water supply and the environment."

WATER SAVING TIPS

  • Put a special bag of crystals in your toilet cistern to save as much as three litres per flush. These can be ordered free from Thames Water on 0845 9200 800.
  • Use the shower instead of the bath. But beware, as power showers can use more than a bath.
  • Fix dripping taps saving of up to 140 litres per week.