Desalination will not help meet water needs, a supplier has found.

After a two-year sea water trial in Newhaven, South East Water concluded it was too expensive and there were too many environmental costs.

It will reconsider if technology improves.

Now, the firm is carrying out engineering studies to see if it can obtain 9.5 million litres of water a day from rocks under the ground at South Heighton, near Newhaven, and near Sevenoaks in Kent.

It wants to fast-track these schemes in response to the drought of 2004-06.

David Shore, operations director, said: "Many technological advances have been made in desalination so it will remain an option to consider as part of our long-term water resources plan.

"However, our trial has demonstrated desalination is not yet the right solution for delivering extra water at peak times or during extended dry periods, such as droughts, particularly when we can potentially get the same amount of extra water from existing, more sustainable, sources.

"Desalination remains an expensive option in terms of operating and environmental costs compared with developing additional resources."

A desalination plant would be expensive to build and maintain, even when not in use.

It would use a lot of power and it would be difficult to dispose of the concentrated salt water produced. Producing one million litres during water shortages would costs £450, compared with £50 for river water and £35 for groundwater.