The Liberal Democrats have highlighted the "potentially horrendous consequences" of environmental damage caused by human activities.

Addressing the Bournemouth conference on Tuesday, environment spokesman Norman Baker said the human race is "conducting a gigantic and unpredictable experiment" with the planet.

He told the party faithful that tackling global warming required urgent action, with this summer's floods offering "a taster of what could be in store" without moves to tackle carbon dioxide emissions.

Baker described climate change as "a weapon of mass destruction" that the government is failing to address.

And also lashing out at the "toxic Tories" he said that under Michael Howard the UK could again become the "dirty man of Europe".

Green concern

Lib Dem policies would encourage greater energy efficiency and promote the use of public transport, Baker said.

And he argued that the party's concern for the environment was not an "add on". "It must run through all we do and all government does," Baker told the conference.

His comments came as the party set out its plans to use tax incentives to promote environmentally friendly behaviour.

Cars that pollute more face higher taxes under the policies, while local councils would gain power to reduce charges for households that cut the amount of waste they produce.

There is also support for a national road charging scheme and a bid to encourage more freight traffic onto the railways.

Managing demand

More controversially, the party also pledges to "manage demand" for air transport, with the aviation industry to pay "the full cost" of the pollution it causes.

The Lib Dems say it will be "bearing down on growth in air travel" by introducing a new aircraft departure duty to price some customers out of the market and encourage the maximum use of each flight.

There is also backing for a plastic bag environment levy, provided the move would cut waste and help to protect the environment.

With younger voters in particular thought to be motivated by environmental issues, the party says it has been "making environmental policies central to every area of policy" in a bid to address their concerns.

"The simple message is that polluters must pay," said Baker.

"But that doesn't mean more tax for everyone, it means a fairer tax system that will financially reward those who use environmental factors in their decision making."

Fly tipping

As the conference continued its debate on green issues, there was also a warning that fly tipping could become a major problem.

Lib Dem spokesman Sue Doughty said a shortfall in capacity meant there is a "massive hazardous waste crisis".

Government failings when implementing the EU's landfill directive meant that there was capacity to deal with just 1.8 million tonnes of such waste while 4.8 million tonnes were actually being produced annually.

Doughty predicted a "huge rise in illegal fly tipping by cowboy waste contractors".