Tony Giddens is an academic, not a politician. But every political party needs a Big Idea. For New Labour, the Third Way is it. And Tony Giddens is Mr Third Way.

More than warmed-up Thatcherism: Tony Giddens on the Third Way

Giddens is involved in all the Downing Street wonkathons aimed at hammering out an intellectual framework for New Labour. "Tony's Tony", as his colleagues at the London School of Economics jokily refer to him, accompanies Mr Blair on all the prime minister's Third Way "summits" with Bill Clinton and his team.

How does 61-year-old Giddens, internationally eminent sociologist, author of a shelf-full of books (31 at the last count) and subject of more than a dozen others, feel about being known as the Third Way man?

Mr Third Way: Tony Giddens was Professor of Sociology at Cambridge before going to the LSE in 1997

"Well I quite like it," he admits. "Because the Third Way is actually the centre of a global dialogue, not just connected with Tony Blair or the position of New Labour in this country.

"Every country that you go to people are talking about it, as it's quite an amazing phenomenon. So I like it, but it does make a lot of work for me."

Part of that work is delivering this year's Reith Lectures for the BBC, starting later this month. The theme of the lectures is "runaway world", the subjects addressed are globalisation, risk in society, tradition and custom, the family, and democracy.

It's been a turbulent few decades for all of these, and this, says Giddens, provides the structural backdrop to the debate over the Third Way.

An ology or an ism?

So what is it, exactly? The Third Way is certainly much talked about in New Labour circles, but what it isn't is more discussed than what it is. It is not old left, corporatist socialism. Nor is it free-market neo-liberalism. But positively defining it in concrete terms has proved difficult - and one of the chief causes of complaint from non-believers.

Is it an ology, an ism? "It's the modernising left," says Giddens. "I mean, you're still trying to follow the same kinds of values, the traditional left-of-centre values. Inclusion, do something about inequality, create a solidary society which cares more for vulnerable people - all those things are still core values.

Bill Clinton and Tony Blair have got together for Third Way wonkathons - and Tony Giddens goes along

"But the new politics says you can't cope with those values, you can't reach them, simply by using the old political ideas. You have to find something new.

"In that debate it doesn't really matter if you use the term 'Third Way', because it has different histories in different countries. For me, you could just substitute 'modernising social democracy'."

At its most basic, then, the Third Way is described as the path between the old left and old right. Sounds simple, really - which is part of the problem.

One size fits all?

The international Third Way brigade includes Germany's Chancellor Gerhard Schröder. He wrote the forward of the German edition of Giddens' book on the subject - The Third Way: Modernising Social Democracy - and would have attended its launch in Bonn a week ago were it not for the little local difficulty sparked by Oskar Lafontaine's resignation.

All around the world: Tony Giddens on how the Third Way is spreading across the globe

President Clinton is a keen Third Way-er, of course. As is Romano Prodi, the former Italian prime minister and current contender to become president of the European Commission.

Not a bad lot to have in your fan club. But critics, of which there are many, remain unimpressed. They protest that the Third Way is little more than trendy sociological waffle so vague as to be meaningless.

First man to the Third Way: Colonel Gaddafi says Tony Blair got his inspiration from the Libyan leader

Take Blair's trip to China last autumn, they say. The prime minister embraced his hosts as fellow seekers for the Third Way and stressed a shared modernisers' agenda between himself and Beijing's ruling free-market Marxists.

And not long after that, up popped Colonel Gaddafi, of all people, claiming Blair had borrowed the idea of the Third Way from the Libyan leader's own writings.

Isn't Giddens' theory an impossibly one-size-fits-all concept? He rejects such talk. The Third Way can apply to very different nations in with very different circumstances, he insists.

"In every particular context you have different policies," he says. "Clearly policies which will apply in the context of the European Union don't necessarily apply in the context of China, or India or Korea.

"But the debate is very similar, partly because of the impact of globalisation itself. We all face a lot of similar problems. What do you do about global financial markets, all the way down to what do you do about increasing equality between men and women and transformation of the family?" he asks. "A lot of these things are now shared in common."

All aboard the bandwagon

Gerhard Schröder: The German chancellor is fan of the Third Way

As confirmation he waves me towards a wodge of cuttings on his desk. "If you look at that pile of stuff over there, those are all articles I've collected from around the world on the Third Way debate, to try and show people it isn't just some kind of warmed up version of Thatcherism."

It is instead "a really systematic discussion about how you reform the welfare state, what you do about the structures of government, how you live in a multi-cultural society, what you do about the gender revolution, how you approach risk scenarios".

Many of these things cannot, he points out, be divided along classical left-right lines.

Some in Mr Blair's own government will take more convincing. A fair few ministers obediently refer to the Third Way in public speeches, only to privately rubbish the notion immediately they leave the platform.

Tony Blair and other Third Way-ers have referred to it as a "work in progress" - an unfortunate choice of words, easily read by sceptics as an admission that they're making it up as they go along.

The only game in town: Tony Giddens on the need for new ideas

Giddens concedes he has probably used the description himself. "That's the sort of thing I do say, yes," he laughs. But he advises the antis to climb aboard the Third Way bandwagon, because no other is going to transport them to political influence.

"Look, for the next years it's going to be the main game in town," he declares. "Because no-one really seriously thinks you can just sustain the ideas associated with the first 25 years after the second world war, which is traditional, bureaucratic, top-down parliamentary socialism. No-one.

Romano Prodi: The former Italian prime minister is another keen Third Way-er

"I don't think anyone thinks you can just persist with those ideas. You've got to change them. Very few people, I think, even on the political right, now think you can just run the world as though it's a gigantic marketplace.

"You've got to find something different from those two. Well, the Third Way debate is what you find, what you look for, what will come from this," he says. "But there's still a lot more work to be done, a lot more thinking to be done."

More liberal than New Labour

Some of his fellow professors at the LSE murmur that Giddens should be wary of compromising by association the college's reputation for rigorous, independent intellectual endeavour by becoming too closely identified with Blair's efforts to develop a theory for his government.

Giddens takes care to distinguish his own Third Way initiatives from his running of the LSE. But he is attracted by the prime minister's openness to radical thinking.

"One of the reasons I quite like being reasonably close to Tony Blair is he does, to me, take seriously that the world has changed in fundamental ways over the past 20 or 30 years," Giddens explains.

"You can't just go with the old ideas, you've got to get new ones. That demands a combination of practical policy-making on the ground from politicians, but also thinking on a wider level and on a deeper level by intellectuals and others working in a network with politicians."

Blair, he is convinced, has "been as keen to work with intellectuals as any other prime minister I can think of in recent memory".

Giddens' views are not identical to Blair's. His own writing reveals him as, for example, rather more of a social libertarian than New Labour.

"It's very nice here": In his LSE office, Tony Giddens does not envisage going to the House of Lords

Bolstering the traditional family is "a non-starter", and he is against making it harder to get divorced. He proposes a moral cosmopolitanism in which "you accept moral values yourself, but you don't impose them on other people".

He is also disagrees with the notion that the best model for equality is "equality of opportunity" - the route to social justice usually cited by Chancellor Gordon Brown.

Regardless of any differences, Giddens doesn't object to being described, the way he always is now, as "Blair's guru". He uses the phrase himself these days on the dust-jacket of his books and in his official potted biography.

I ask the guru what he thinks he'll do in the House of Lords when he gets there. "I'm not going to be in the House of Lords," he guffaws.

Is he serious? Tony's Tony, house intellectual to Number 10, not in line for a probable eventual peerage? "Not as far as I know," he insists.

What hypothetically would he do there, then? "Mmm, I'd worry about that when it comes."