Balancing the books - do we need a new law?

Why pass a law to force yourself to so something you already intend to do? That was my first reaction to the news that the chancellor plans to legislate to oblige him to run a budget surplus in "normal times" - in other words to raise more in tax than he spends when the economy's not in recession.

So, is this announcement pure politics? After all, George Osborne knows that the first rule of political strategy is to "define your opponent before they can define themselves".

By announcing this now but delaying a vote on it until the Autumn he is ensuring that the argument about spending will dominate the Labour leadership campaign and that the new Labour leader will have to decide whether to vote for or against balancing the books.

This, though, is about more than merely wrong-footing Ed Miliband's successor. Osborne is trying to alter the rules of the political game permanently - or, as Gordon Brown would have put it, to create a new consensus. He wants running permanent deficits to be as politically unthinkable as pledging to scrap the minimum wage or oppose gay rights.

However, don't allow all this politics to distract from an important economic debate about whether it is sensible prudence or ideological madness for a government to balance the books.

After all, many of us borrow to invest ie we have a mortgage to buy our houses and governments can borrow more easily and more cheaply than individuals so why shouldn't they do the same ie borrow, even in good times, to build houses, roads or hospitals?

What's more borrowing can, many economists argue, increase the rate of growth and, therefore, cut deficits and debt faster than aiming to do so by cutting spending.

Whoever is right, many in politics now see the argument for more rules to limit politicians' freedom to act irresponsibly and less discretion for them. Not so long ago ministers could rig interest rates for political reasons. They could tell the Bank of England what to do. They could alter economic forecasts to make themselves look better.

The independence of the Bank of England and the creation of the Office for Budget Responsibility have put paid to all that. So, the answer to my opening question may be that that's the best way of ensuring that our leaders do what they say they mean to do.