In his interview with the Economist, Tony Blair seems like a sad old man living in the past. He says that "the Labour Party succeeds best when it is in the centre ground" - something which entails "not alienating large parts of business, for one thing".

What this misses is that things have changed since the 1990s. What worked for Labour then might well not work now.

What I mean is that in the 1990s Labour could plausibly offer positive-sum redistribution and could therefore please both left and right. Take for example expanding higher education. This was leftist - because a higher supply of graduates would bid down the graduate premium and hence help reduce inequality. But it was also rightist because it improved skills and opportunity. Or take tax credits and minimum wages. These were leftist because they reduced poverty, but also rightist because they encouraged work. Similarly, the promise of policy stability was intended both to please business and to encourage job creation.

Such policies were centrist, vote-winning and (within limits) reasonable economics.

However, we don't live in the 90s any more. There are at least five big differences between then and now.

1. In the 90s, New Labour's centrist policies were consistent with mainstream economics. There was a decent overlap between good politics and good economics. This is no longer the case. The political centre supports austerity and tough immigration controls. These are not just inhumane but economically illiterate. The political centre and the economic centre are two very different things.

2. If positive-sum redistribution is at all feasible (and it is an if) it consists in wage-led growth. This is not especially politically centrist.

3. The danger for Labour is no longer merely that voters will leave it for the Tories for fear that it cannot be trusted on the economy. It's also that they won't vote at all or will switch to Ukip because they fear Labour is insufficiently anti-establishment and too centrist; Ukip supporters, remember, overwhelemingly support (pdf) price and rent controls and nationalization. They want a government that alienates business.

4. New Labour thought that managerialism would increase efficiency in the public and private sectors. However, with productivity stagnating in both public and private sectors, the evidence now tells us that this is not the case and that, instead, managerialism is an ideological cover for the enrichment of a minority. Policies to increase equality and efficiency must, therefore, challenge managerialism.

5. In an era of secular stagnation, macroeconomic stability - even if it can be achieved which the experience of 2008 suggests is not possible - is not sufficient to boost investment, innovation and growth. Perhaps, therefore, greater intervention is necessary.

My point here is that Blairism should not be rejected (merely) because it is insufficiently left-wing as Neal Lawson claims, nor (just) because the centre ground is a "nonsensical chimera" as Phil claims. Instead, it should be rejected on the purely pragmatic grounds that the economy has changed since the 90s and so we require different policies. In failing to say this, Blair appears to be an irrelevant out-of-date ideologue.