Gordon Brown's mud-slingers eat humble pie (Not that bad-mouthing is confined to Labour. Matthew d'Ancona, in his book on the Coalition, In It Together, recounts numerous stories of Steve Hilton, adviser to David Cameron, who screamed: " You ----ing lied!" to Sir Bob Kerslake, head of the Civil Service.) Yet 15 years later, here is Mr Balls calling for his figures to be verified by the very man who found him out in the first place. What is more, the OBR was set up by the Coalition in 2010 precisely to ensure that politicians - such as Messrs Brown and Balls - would never again be able to fiddle the all-important Treasury forecasts on which economic policy hangs. I put it to one insider that forecasts are always a matter of judgment, and it might have been unfair to accuse Gordon Brown of cooking the books. He paused. "Unfair?" he asked. Not when the numbers are being shaped by phone calls from the Brown team at three o'clock in the morning on the day of the Budget. Labour's Alistair Darling, in his book Back from the Brink, reports that when he was at the Treasury he had endless disputes with Mr Brown over the forecasts. "I wanted our growth projections to be above all realistic," he writes. If they weren't, no one would believe anything we had to say. As always, Gordon thought I was being too pessimistic. The very existence of the OBR is a reproach to the way the likes of Mr Balls ran the Treasury. So could the OBR look at Labour's policy costings in the same way it looks at those of the Government, and so make an honest man of the shadow chancellor? Certainly, such a move would put the economic policies of the major parties on a more equal footing. And whatever the friction years ago, Mr Chote himself would not be averse to the idea. Last year he told the Institute for Government that he thought it would be "good for politics," though it would require a huge expansion in staff numbers. The OBR has 17 people, a similar body in Holland has 150, and the non-partisan US Congressional Budget Office has nearly 250. Until Parliament reviews the OBR in 2015 - after the election - the office is banned from working with other parties. Yet the possible expansion of its role raises wider issues. No one would question the rigour and integrity of Mr Chote and his staff, but they are of course unelected. And the last few years have seen a tendency for politicians, particularly Labour, to bring in unelected outsiders to lend authority and credibility to their policies. Think of Lord Darzi in health, Admiral Lord West in defence, Lord Malloch-Brown in foreign affairs. Yet experts and outside bodies can get it horribly wrong. Only this week, the IMF was forced to double its growth forecasts for the UK - much to the satisfaction of George Osborne and the Coalition. Perhaps the move to import more "experts" into government - there are plans to bring more of them in to staff ministerial offices - is a sign of how far politicians are losing confidence in their own ability to convince the public of their competence and probity. Tales from the last few years of how badly some of them behave in government will make winning public trust a long haul.