Leading article: Still leaders in the quest for green solutions

First the Government pledged a 60 per cent cut in the UK's carbon emissions by 2050. Last week a Conservative policy review group proposed a reduction of 80 per cent. And yesterday, the Liberal Democrats trumped them both by voting for a target of cutting emissions by 100 per cent by the middle of the century. The green "arms race" between the main political parties is accelerating. This is encouraging for all those who, like this newspaper, have long called for environmental protection to be at the heart of the UK political debate. But long-term targets are one thing, credible policies quite another.

In this respect, the Liberal Democrats, who are holding their annual conference this week, have much to be proud of. They went into the 2005 general election with easily the most environmentally conscious manifesto of any of the main parties. And last year they unveiled their "green tax switch", which proposed that revenues from new taxes on polluting behaviour should be used to cut taxes on income. This is an approach now being co-opted by the Conservatives.

But politics does not allow any party to rest on its laurels. The Conservatives, and to a lesser extent the Government, have been catching up with the Liberal Democrats on the environmental front. In recent months the party has been squeezed in the battle for the green vote.

Yesterday's conference motion from the environment spokesman Chris Huhne was a largely successful attempt by the party to reclaim leadership of the green agenda. The proposals demonstrate an understanding that tackling transport – which accounts for a fifth of our emissions – is essential. The party is now committed to charging lorries to use the UK's road network and channelling the funds into the rail network. This will have the double advantage of discouraging the movement of freight by road, and making it more attractive for companies to move goods by rail.

There is little doubt now that the hidden subsidies given to the airline industry are unjustifiable. Yesterday's proposal of a £10 "climate change levy" on domestic flights is certainly one way of redressing the balance. The target of phasing out petrol cars by 2040 is ambitious – but by no means unachievable if the necessary investment in biofuels and alternative forms of transport are pushed through.

The proposals are also pleasingly robust on cutting emissions from energy production. Paying a higher rate to those who export energy to the National Grid would give a much needed boost to micro-generation. And Mr Huhne is right that central Government needs to set its sight for renewable energy a good deal higher. A target of 100 per cent of UK energy production to be sourced from renewables by 2050 will certainly be difficult to achieve – but that is precisely the kind of radical switch necessary if we are to slow the process of climate change. Other ideas such as the creation of an international fund to help developing countries adopt low-carbon technology and mortgages that encourage energy conservation also have much to be said for them.

So the Liberal Democrats are once again at the forefront of the environment policy debate. But they also deserve credit for demonstrating an understanding of the immediacy of the threat of climate change. The motion yesterday argued that "if decisive action is not taken in the next decade, any prospect of a stable climate may be lost". We have yet to hear a similar sense of urgency articulated by either David Cameron's Conservatives or the Government. They may have their difficulties at the moment, but while the Liberal Democrats champion the environmental cause with such vigour they will continue to have currency in British politics.