The Liberal Democrat leader has called for environmental issues to be at the heart of the next general election campaign.

In a keynote speech on Tuesday Charles Kennedy set out a twin-pronged approach to green issues.

He called on Tony Blair to involve the US in a global push to reduce the carbon dioxide emissions that cause global warming.

And he said a range of new policies were needed in the UK to put environmental thinking at the heart of government.

Kennedy said his party was committed to a Britain "in which a green thread runs through government policy".

Beyond Kyoto

Kennedy told environmentalists it was time to "look beyond the Kyoto treaty to the next stage of the battle to limit climate change".

The Lib Dem chief said that while the environmental community was "unenthusiastic" about the re-election of George Bush, the American administration had to be involved in efforts to tackle climate change.

Kennedy said contrary to many perceptions action to reduce pollution was being taken in the US.

But he warned "it would be disastrous if the president's new mandate allows such voices to further undermine international efforts to achieve real consensus".

With Britain holding the G8 presidency in 2005, Kennedy said the prime minister should seize the opportunity to bring the US into negotiations on the environment.

"I want him to focus specifically on bringing the United States into the consensus so that it becomes a part of the international solution," Kennedy said.

"It should be the prime goal of the British prime minister to secure public agreement from the White House that the science of climate change is real and the threat is real.

"He must achieve agreement that the US will engage, not just as an observer, but as a participator, in the next round of climate change negotiations, known as the Conference of Parties in autumn 2005."

Domestic plans

Turning to domestic policy, Kennedy said Labour had failed to give environmental issues a high enough priority.

He said that government hopes of reducing carbon dioxide emissions by 20 per cent compared with 1990 levels by  2010 were looking "wholly unachievable".

"Let us be under no illusion about issues relating to the environment. I don't believe failure can be an option. The stakes are too high," the Lib Dem leader warned.

He also denied that his party's policies were about "punitive" taxes on consumers and energy users to force changes in behaviour.

"The Liberal Democrats would use environmental taxation as it is supposed to be used," Kennedy said.

"We are not proposing higher overall taxes but using existing taxes to reward environmentally friendly behaviour.

"But we are proposing to establish an environmental incentive programme with the aim of ensuring that the polluter pays the full environmental costs of any polluting activities.

"But pursued on a tax-neutral basis with revenue recycled into offsetting tax cuts."

Treasury issue

A Lib Dem government would also "put the environment at the heart of the treasury", Kennedy added.

"The environmental incentive programme should cover subjects such as energy, surface transport, air transport, land use and waste management, and also address public subsidies for unsustainable activities.

"The revenue from these taxes will not disappear into a bottomless pit within the treasury but will be fed back into lower taxes elsewhere."

The party's plans include a new aircraft departure duty to boost incentives to maximise the use of each flight, and giving incentives for more environmentally friendly road vehicles.

"My challenge to the other political parties is to match our commitment," Kennedy concluded.

"Because if the environment is ignored at the next general election, our political process is devalued.

"And those who will suffer most are those who can't vote at present - the next generations to whom we will be bequeathing a poisoned legacy.

"I am determined that we do all we can to stop that happening."