The UK is to commit to a big shift towards cleaner forms of energy, Tony Blair has said.
The government wants to focus on renewable energy
The prime minister's key-note speech coincides with the publication of a long-awaited White Paper detailing plans to radically cut pollution blamed for global warming.
He said that Britain will agree a goal of a 60% reduction in carbon dioxide emissions by 2050.
Mr Blair also rejected calls for new nuclear power stations and said he wanted to concentrate on encouraging use of renewable energy, such as wave and wind power.
But the Conservative Trade and Industry spokesman, Tim Yeo, has said he is worried that the UK will end up more reliant on energy from abroad.
The White Paper suggests that 10% of electricity should come from renewables by 2010 - up from 3% now - with an "aspirational goal" of 20% by 2020.
Measures to cut down on the amount of energy actually used, or wasted, are also proposed.
Earlier, Energy Minister Brian Wilson told the BBC that the White Paper signalled "a good day" for the environment, although the UK would have to work hard to meet the goals.
He said: "We have a firm existing target for renewables to make up 10% of electricity in the UK by 2010 and we say we should be aiming to double that by 2020.
"Ten per cent by 2010 is a challenging target."
But some analysts have thrown doubt on whether targets, particularly those on CO2, can be achieved without nuclear energy.
Britain's 16 nuclear power stations will all reach the end of their working lives in about 30 years.
Environmental groups have welcomed the move away from nuclear power.
A spokesperson for Friends of the Earth said: "The White Paper will hopefully sound the final death knell for nuclear power in Britain."
Some householders as well as the nuclear industry may be disgruntled by the proposals, which will add to electricity prices.
The paper says the new policies will add between five and 15% to household electricity prices, up to 25% to industrial electricity prices and up to 30% to industrial gas prices by 2020.
Energy Saving Trust chief executive Philip Sellwood said: "The government is right not to invest in nuclear.
"We welcome the government's confirmation, that in the words of the White Paper, the cheapest, cleanest and safest way of addressing all our goals is to use less energy.
"By making the right investment decisions now we will ensure that the White Paper delivers on its objectives."
Coal and gas
Coal, which fuels about 35% of the country's power stations, will continue to play a role in
Britain's energy mix, although the emphasis would need to be on cleaner technology, says the paper.
Gas, which is cleaner and accounts for more than a third of the energy mix, will also continue to play a key role and the government will need to ensure it secures future supplies from foreign markets, according to the White Paper.
Sir Bernard Ingham, secretary of the Supporters of Nuclear Energy group, said the government's "so-called" energy policy was no answer to Britain's needs.
He accused them of avoiding the policy which was staring it in the face - developing nuclear power.
"As the Royal Society has pointed out, intermittent and unproven renewable sources of energy are no answer to Britain's needs for reliable, continuous electricity."
Analysts have also expressed concerned that by 2010 the UK is on course to be a net fuel importer, for the first time since the industrial revolution - which brings political and economic implications.