In March's Budget, Chancellor George Osborne cut the top rate of tax from 50 per cent to 45 per cent. Mr Osborne is under pressure to go further and slash the top rate of tax to 40p, however Lord O'Donnell suggested this would lose the Exchequer too much money. Instead he suggested that the top rate of tax should hover around 48p, as small print in Budget documents had showed this was the rate which maximised tax revenues. He told The House magazine: "What struck [me] was the - it's buried away in a footnote - solution to one of the all times biggest problems that economist have faced, which is 'what's the income tax rate which maximises revenue?'. And there it is, nobody's mentioned it really, it's there in a footnote: 48 per cent. That's what's there in the OBR report. Asked if this meant that 45p is, for revenue-raising purposes, as low as any sensible government would go, he replied: "It would suggest that under that model a move to 45 to 40 would have a very large cost, that's right." Lord O'Donnell also said he would like to be Governor of the Bank of England. Last month The Daily Telegraph reported that Lord O'Donnell was in the running to be the next Governor, replacing Sir Mervyn King who stands down after a decade in charge in Threadneedle Street in 2013. From early next year, the Bank is taking on new regulatory roles from the Financial Services Authority, as well as other powers over interest rates and to intervene in the supply of credit and lending to households and companies. The changes have led some observers to say the next Governor will be one of the most powerful unelected officials in Britain. Lord O'Donnell said: "I'm going to think about that and make a decision nearer the time. You'd need to think about how you manage that and what support you'd need. George Osborne, the Chancellor of the Exchequer, is due to unveil the external recruitment process to find the successor next month. Lord O'Donnell also took a swipe at ministers" political advisers, criticising them for being inexperienced and too shallow. He said: "My criticism would be [that] it's not so much about numbers, it's about backgrounds. Too many come from a media, sort of PR background. What I'd like are some special advisers who are real experts in the subject. When you see the good ones, you know them. They've got to be in that ground between policy and politics and get both sides of it. Lord O'Donnell also shed light on the origins of his "GOD" nickname, suggesting that it was a help in asserting his authority sometimes. He said: "I initialled something G.O.D - it was ages ago, back in the Treasury, a long, long time ago. It's just one of those things you just get stuck with. There are times when you want to be clear about your authority, so it can help, yes.