It’s been pouring down all day when I meet Nigel Lawson, and I mention this as small talk while we sit down. He smiles at me almost mischievously. “Caused by global warming, no doubt,” he quips. The veteran statesman has an amusing irreverence: he was missing the House of Lords’ debate on the Copenhagen conference to be in Cambridge.

Behind the charm there’s a steel core. Lawson has done all the right things to make himself into many people’s bogey-man. He led the Thatcher Government in its bloody battle against the miners whilst Energy Minister and, as Chancellor of the Exchequer, he presided over privatisation and financial deregulation – now a dirty word. His latest claim to fame is his vigorous scepticism about the environmentalist movement.

Yet a lot of what is said about Baron Lawson of Blaby is rather inflammatory. People often think that he denies the facts of climate change, but if you read his latest book An Appeal to Reason: a Cool Look at Global Warming, his arguments are more subtle. Lawson believes that global warming is happening, but that its effects won’t be as severe as most people think. He may have contributed to the 2007 documentary film The Great Global Warming Swindle, and rejected many of the findings of leading scientists on the Intergovernmental Panel on Climate Change (IPCC), but he’s not some British red-neck gas-guzzler who rejects the whole idea because it’s inconvenient.

Lawson’s got a lot more to talk about than climate change too. I start by asking him if Cameron’s Conservatives deserve to win the next election.

“I think certainly there’s no doubt the present Government deserves to lose. Which means, I suppose, the Conservatives deserve to win.”

I press him further on the matter. He’s a Conservative old guard, and David Cameron’s portrayed himself as the heir to Blair. Does Lawson actually like Cameron’s policies?

“The heir to Blair was what he was originally; he’s edged away from that a little, but in terms of his style of politics he’s very much Blair.” Hardly a ringing endorsement.

But Lawson vehemently condemns Labour’s record in power. “This is a government that has allowed the public finances to get in a terrible mess,” he declares. “The economy was in good nick when they came into power in 1997, and it is now in a terrible state.” He argues the unprecedented debt we are in has a “structural element”.

“If you look at this Government, they are pretty exhausted; they haven’t got the will or the capacity to take this country forward.”

I challenge him that while he was Chancellor of the Exchequer he was responsible for a great deal of financial deregulation; there’s an argument that deregulation contributed to the banking crisis. Lawson is completely self-assured on the matter. “I think we would not have been in as big a mess as we are on the banking side of things if Gordon Brown had not dismantled the system I put in place and replaced it with another system, which proved dysfunctional.”

Commercial banks, because of their importance to the economy, are bailed out by the taxpayer if they fail, Lawson says; not so with investment banks. Even if the Brown system could have been made to work, Lawson declares, “the regulators were asleep on the job.”

“What they were obsessed with was the need for consumer protection. That’s important, but it is not the most important element. If [banks] are allowed to take such risks in the belief that they will be bailed out by the taxpayer then you’re not doing your job.”

Inevitably, we do move onto global warming. Lawson tells me that though some politicians may believe in the science, to be seen to be tackling climate change is pre-eminently just a box to tick for voters. “It has become a new secular religion which you have to subscribe to,” he proclaims, “and if you don’t you are evil and wicked; it is like political correctness.”

You have to judge the scientific case that Lawson makes in his book for yourself. His arguments are lucid, with a penchant for fruity sound bites. Climate change is like the Da Vinci Code, he writes: “it contains a grain of truth – and a mountain of nonsense.”

But his book was written two years ago now, and I challenge him that some of what he said is out of date. For instance, he wrote that the Chinese Government will not accept targets to reduce emissions. He cuts me off. “Which proved to be right. That’s one of the reasons why the Copenhagen conference was a complete fiasco. If that was obvious to me in January 2008, it is astonishing that politicians’ grasp of reality was so tenuous that they went flying ahead.”

But wait: last autumn, Chinese leaders announced new targets for reducing carbon emissions, which, if met, would put the nation in the lead on combating climate change by 2020. They have created a £134.4 million green-stimulus package, and are the biggest producers of solar technology.

Lawson is cynical. The Chinese merely see a good market in solar panels, he suggests. “They have said nothing about emissions reduction, they have said something they think will fool people.”

We are misguided in our obsession with green living and recycling, in the Lawson view. But isn’t there something inherently virtuous in being less wasteful, I ask?

Lawson agrees, especially with regard to water, but he changes the topic: “it’s a question of what is going to be the cost of pursuing the sort of policies that we are told we must, and that cost is absolutely prohibitive.” He’s not being cynical now, but moralising. Thirty million Indians need electricity to lift them out of poverty and the cheapest way to give them that is carbon energy, he argues. “If you try and stop that then you are condemning tens and tens of millions of people to unnecessary poverty, unnecessary malnutrition, unnecessary disease, and unnecessary premature death.” He concludes: “this [environmentalist] policy which we are told we must pursue, when it comes to the developing world, is in my opinion a thoroughly wicked one.”

He may be nearly eighty, but Nigel Lawson could still prove very influential yet.