The new London Mayor Boris Johnson today dropped a legal challenge by his predecessor against a treatment plant which would turn salt water into drinking water.

Ken Livingstone launched the High Court challenge last year against the £200 million desalination plant at Beckton which aims to ease water shortages in the South East.

Mr Livingstone had claimed cleaner, cheaper and less wasteful alternatives should be found to the "energy-guzzling and carbon-intensive" plant, which had been given the go-ahead by the Government.

But today, his successor Mr Johnson said he had agreed to withdraw the legal challenge to Thames Water's plans for the desalination plant in return for a series of environmental measures from the company.

They include working to help reuse waste energy generated from the proposed Barking Power Station to provide heat and hot water for up to 90,000 homes, along with a range of water efficiency measures.

Thames Water has also said the generator used to power the energy-hungry plant will use 100% renewable fuel, initially in the form of biomass such as locally sourced rape seed oil.

In addition, the Mayor said Thames Water had committed to working to reduce the impact of road works on traffic in London.

Mr Johnson said: "We cannot risk London running out of water at times of drought, but this cannot be at any cost.

"Thames Water has satisfied me that the desalination plant will minimise its impact on the environment by using renewable energy, and by being used only when absolutely necessary."

Thames Water welcomed the decision to drop the High Court appeal against the treatment plant on the north bank of the River Thames at Beckton, east London,

The company's chief executive David Owens said the news was a victory for common sense, as London's growing population would need more water.

"The desalination plant is a vital part of our response to this situation, and we are committed to getting it built as quickly as possible, so it is available to provide more safe, clean drinking water to Londoners by 2010.

"Desalination is a more energy-intensive process than conventional water treatment processes, which is why we have committed to only running the plant when it is essential, and to providing 100 per cent of the power needed to run it from renewable energy," he said.

But Darren Johnson, Green Party member of the London Assembly, said: "This desalination plant is a waste of energy, a waste of money and will encourage Londoners to keep wasting water.

"Building the desalination plant is the kind of short cut which we have come to expect from Thames Water.

"Instead of spending money on this energy-wasting, short-term solution, they should be investing in fixing pipes and stopping leaks."