With one eye on the green vote, the main candidates have been promoting
their ecological credentials at a Reuters newsmaker event in London. Reporter
Darcy Lambton has more. 

The finishing line is almost in sight in the fiercest battle yet to become
London Mayor.

And in this campaign green politics have moved centre stage like never
before.

That's again been in evidence at a Reuters newsmaker event for the leading
candidates.

Mayor Ken Livingstone says climate change poses a huge risk to London's
future.

SOUNDBITE: Mayor Ken Livingstone, saying (English):
"I think we may actually have passed the tipping point of
irreversible climate change. And I think we're heading into catastrophic
violent weather by the middle of this century and therefore everything must be
done to reduce carbon emissions." 

Since becoming London's first elected Mayor back in 2000, Livingstone has
made his environmental mark.

To help reduce emissions he introduced a traffic congestion charge, now
reportedly the largest of its kind in the world.

Entry into the zone costs motorists eight pounds per day and the scheme has
caught the eye globally.

Critics question Livingstone's decision to extend the zone westwards which
they say hurts small businesses.

His main election threat is the Conservative Party's Boris Johnson who is
something of a local celebrity,

Famous for cracking jokes, opponents often call into question Johnson's
credibility as a serious politician.   

Livingstone says Johnson would be a disaster for London in the fight
against climate change.  

In response Johnson has slammed the Mayor's latest plan to hit the biggest
gas--guzzlers with a 25 pound congestion charge.

SOUNDBITE: Boris Johnson, Conservative Party Mayor candidate:
"Actually according to a study for Transport for London it might
even increase emissions. So it's environmentally trivial, it's gesture
politics designed to show that this Labour Mayor is an old fashioned sod the
rich kind of guy at heart."

As you might expect, Livingstone believes his leadership on the environment
merits a third term.

On May the first, voters will let him know if they agree or not.

But whatever the outcome, it's clear the environment is no longer the
marginal issue it once was in London's political life.

Darcy Lambton, Reuters.