Mervyn King, the governor of the Bank of England, is among the world’s most influential central bankers and leading policy economists. I greatly admire both his intellect and his integrity. Mr King has also played a big part in persuading the UK’s coalition government of the urgency of what he calls “a clear and credible plan for reducing the deficit”. To his great credit, he has just said this to the Trades Union Congress, the most unfriendly audience he could find. He went on to say: “I would be shirking my responsibilities if I did not explain to you the risks of failing to do so.” Indeed, he should say what he thinks. But is he right to think as he does? I have doubts.

That will come as little surprise to those who read my endorsement of points made by Ed Balls , former adviser to Gordon Brown and current Labour leadership candidate, two weeks ago. I am more fiscally hawkish than Mr Balls, as I said at that time. But I am not as hawkish as Mr King. Yes, I agree that there are risks to cutting the fiscal deficit too slowly. However there are also risks in cutting it too fast. Similarly, while there are risks in not having a credible plan, there are also huge risks in having an inflexible one. The UK needs an adaptable plan for fiscal cuts, one that takes account of the huge uncertainties that result from the fragility of the private sector.

What is the core of Mr King’s argument? It is that “market reaction to rising sovereign debt can turn quickly from benign to malign ... It is not sensible to risk a damaging rise in long-term interest rates that would make investment and the cost of mortgages more expensive. The current plan is to reduce the deficit steadily over five years – a more gradual fiscal tightening than in some other countries. As a result of a failure to put such a plan in place sooner, some euro-area countries have found – to their cost – a much more rapid adjustment being forced upon them.”