Gordon Brown’s carrot may amount to a shrewder reading of public opinion than David Cameron’s stick. Voters are now green in principle, but only ambiguously so in practice. Most want to save the planet, but are dubious about paying higher taxes.

There is no distinct green vote. Voters cannot be so easily segmented. Most of us have several, often conflicting, identities and interests. Of course, a small minority of voters care so passionately that they back the Green Party, about 4 per cent or so according to recent polls (more, incidentally, than support the UK Independence Party or the British National Party). In general, however, greenery is more a matter of attitude than of partisan affiliation.

Mr Cameron is correct that British voters are now concerned about climate change, and he has skilfully identified with that mood. According to YouGov, 85 per cent of the public think that global warming is taking place and almost as many believe that, unless action is taken, global warming will accelerate.

Voters think of themselves as green. A Populus poll for The Times in November showed that four fifths claim to boil only as much water as needed and to switch off the television by using the off button, and two thirds say they buy only low-energy light bulbs. These claims are way ahead of the reality.

Once you move from rhetoric to detail, however, voters become more sceptical. Despite a bias in favour of appearing green, the public is split 53 to 45 per cent on being willing to pay significantly higher petrol prices, car tax and air fares as part of efforts to cut back carbon emissions.

According to Populus, seven in ten say that introducing new green taxes on petrol and airline tickets would only be acceptable if other taxes were cut.

As Peter Kellner, of YouGov, has argued on The First Post website, people like low-cost proposals and ones that punish other people; they do not see why the British should act, and pay more, unless big polluters around the world also cut emissions; and we do not trust politicians to use the money from raising green taxes to reduce other, direct taxes.

They fear that the overall tax burden would rise: hence the public hostility to the recent rise in air passenger duty.

That is why the Liberal Democrats’ package last September was presented as tax-neutral overall with large rises in direct taxes balanced by cuts in direct taxes.

The Tories have so far been bolder in their commitment to action, notably with their weekend proposals for taxing frequent fliers. The party has promised that the tax burden will not rise, but spokesmen have not yet said which taxes will be cut.

Conservative supporters are, however, more sceptical than those of other parties about measures to tackle climate change. Some senior Tories question the extent of the threat.

Mr Brown has avoided such pitfalls with his plans to extend insulation and to phase out high-energy light bulbs. While Mr Cameron has so far taken the risks, the challenge for the Government is show whether their incentives, and today’s draft Climate Change Bill, are tough and specific enough to reduce carbon dioxide emissions by 60 per cent by 2050.

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