Leading article: Were those huskies hugged in vain?

When did David Cameron betray the green cause? This might be an A-level politics question in years to come. Was it when the departure from Downing Street of Steve Hilton, the Prime Minister's strategy adviser who devised "vote blue, go green", was announced last week? Was it when Chris Huhne stood down as Secretary of State for Energy and Climate Change last month? Or was it when George Osborne, the Chancellor, said, "We're going to cut our carbon emissions no slower, but also no faster, than our fellow countries in Europe", in his party conference speech last October?

In his first interview as Mr Huhne's replacement, Ed Davey tells us today: "Let no one be under any illusion, I am completely committed to the ambition for this to be the greenest government ever." Well, the new Climate Change Secretary must forgive us for wondering what is illusion and what reality.

We do not doubt his sincerity or his ability, but, under the British constitution, a coalition is an imperfect constraint on prime ministerial power. Nick Clegg, the Deputy Prime Minister, discovered the truth of this in its most stark form in the early hours of a morning in December, when he was telephoned to be told that Mr Cameron had said "no" to the European fiscal union. Mr Davey must know that his ambition to "transform the energy and climate change position of the country" will count for nothing if the Prime Minister has lost interest, or if the Prime Minister's interest is intermittent and headline-driven. As Mr Davey tells us today, in relation to balancing energy costs against conservation: "It's easy to say but difficult to do." And impossible to do without sustained prime ministerial support.

Sadly, it would seem that Mr Cameron's greenery was mere pre-election positioning, and the "greenest government ever" pledge the product of post-election euphoria. This newspaper feared as much, but we were prepared to give Mr Cameron the benefit of the doubt, partly because the Labour Party provided such a grey alternative. At the election, the main difference between the parties was that the Tories promised not to build a third runway at Heathrow. This gave Mr Cameron just enough green cover to carry off his opposition husky-hugging hustle.

Since the election, however, the green rhetoric has faded, despite aggressive attempts by Mr Huhne to keep the colour toner cartridge filled. Economic austerity has been used as an excuse by Mr Osborne for eschewing a leadership role for Britain in developing low-carbon technology. If Mr Cameron really wanted to show leadership, the recession could have been a green opportunity, because lower economic activity will have cut carbon emissions and made it easier to hit carbon reduction targets, while insulation work would have been a better stimulus to the labour market than unpaid work experience in supermarkets.

Unfortunately, in the absence of green leadership from the Prime Minister, the centre of gravity of the Conservative Party has been sliding back to climate-change scepticism. This retoxification is surprising, given the central role in Downing Street played by Steve Hilton, who was the guru of green Toryism in opposition. But, as John Rentoul points out today, Mr Hilton has joined the sceptics, telling friends that he is "not convinced" that global warming is caused by human activity.

Perhaps, then, his departure for the land of high energy consumption might be good news for green policy? We think it unlikely. In his speech to the Conservative spring conference yesterday, Mr Cameron seemed to be trying to offset the departure of his impatient reform-minded adviser by claiming that he did not come into politics to "play it safe". But beyond saying "we have got to reform the planning system" – which implies an Osbornian view that growth and greenery are in conflict and that growth must take priority – the environment failed to get a mention.

All is not lost, if only because Mr Cameron should be embarrassed to be so obviously reneging on such extravagant promises so publicly made. But the Prime Minister needs to face down the backward-looking elements in his party who reject the science of climate change. Indeed, if this government is to have any claim to be green at all, he must give the new Secretary of State for Energy and Climate Change his full and consistent support.