Ken Livingstone, the Mayor of London, complained today that his attempts to persuade Londoners to flush less water down their toilets had been complicated by the fact that Thames Water's German owners preferred not to talk about the subject.

Mr Livingstone made the comment at the Labour conference in Manchester, where he called for a £10-£15 levy on plane tickets to tackle global warming and the pollution problems caused by air travel.

The London Mayor said that Londoners had reduced their water consumption by around 8 per cent during the recent shortages and said that compulsory water metering was now inevitable.

"I think Londoners are ready to say we must meter our water. I am quite happy if the Government want to devolve power to me I'll do it," he said.

Mr Livingstone told delegates that a third of water in homes is flushed down the toilet, and repeated his call for people to help cut water usage: "You really don't need to flush the toilet when you have just had a pee."

He said he had approached Thames Water about promoting the idea but he was told the company's owners, RWE, were German and were not keen on talking about toilets in public.

"You can't mention the War or flushing the toilet," he joked.

Mr Livingstone admitted that the debate on air travel was politically sensitive but said that it needed to be addressed urgently.

"It's the single most difficult thing. We are not going to be able to put that off much longer," he said. "Aviation has got to be brought right to the centre of this debate."

At the moment, Mr Livingstone, many of the benefits of reduced carbon emissions were being cancelled out by the growth in cheap flights.

"While Government and cities have been pressing to reduce carbon emissions, all that we save is being taken up by the increase in air travel," he said.

"In the next election we must have a serious debate to ensure we get a commitment from the British people that the environmental cost of air travel is reflected in the price. I believe people are ready for that - people are ready for substantial change."

Shortly after he spoke, David Miliband, the Environment Secretary, announced an initiative that he said would unlock half a billion pounds of investment into renewable energy projects across the UK.

The scheme, to which the Government will contribute £10 million, is designed to encourage the construction of alternative energy projects, mostly wind turbines, on land owned by local authorities, health trusts and other public bodies.

By leveraging private investment, the projects involved should be producing 500MW of electricity within five years, enough to serve the houses of Norwich, Oxford, Exeter and Newcastle combined while avoiding up to 190,000 tonnes of carbon emissions.

"At the moment we are living, Britons in the 21st century, as if there are three planets to support us when in fact we have only got one," Mr Miliband said.

"We are consuming the natural resources of three planets - burning the fossil fuels of three planets, pumping out enough carbon dioxide for three planets, yet we only have one planet to live on. The challenge is immense. But so are the tools at our disposal."

Times Recommends

• An officer and a gentle woman
• Dame Helen Mirren is worthy of the Epidaurus
• Foods that can help to prevent swine flu