Leading article: A populist blunder from Mr Cameron Perhaps it was because David Cameron felt he was not making much of an impression at the G20 summit in Mexico that he could not resist jumping on a passing domestic bandwagon. Whatever the reason, the home audience was treated to the spectacle of their Prime Minister, at a gathering of world leaders, discussing the personal finances of a stand-up comedian. Jimmy Carr's tax-avoidance arrangements were, he said, "quite frankly, morally wrong." But for the sake of one good headline, Mr Cameron has created a problem that will see out his Conservative leadership. After all, Mr Carr is by no means the only high earner whose tax arrangements could arguably be called "morally wrong." Most of the very wealthy do all they can to avoid tax legally - including a number of well-known Tory donors. One good example is Lord Ashcroft. The Tory peer, who has given the party £6m and was Mr Cameron's deputy chairman for five years, spent a decade refusing to talk about his tax arrangements before admitting that he was a non-dom. Notably, Mr Cameron's response was that "Lord Ashcroft's tax status is a matter between him and the Inland Revenue." It seems the Prime Minister was soon aware of his blunder this week. Asked, on his return from Mexico, about Take That star Gary Barlow's alleged tax avoidance, Mr Cameron's previous volubility disappeared. It would not be "right," he said, to "give a running commentary on different people's tax affairs." What a mess. And it is one entirely of Mr Cameron's own making. Most worrying of all is that this latest debacle is just one of a series of unforced errors which, taken together, only add substance to concerns about the Prime Minister's judgement. Not only must he take a share of the blame for the string of policy climbdowns that followed the Budget. There are also the questions raised by the hiring of Andy Coulson, the promotion of Jeremy Hunt to judge on the BSkyB deal, and the Prime Minister's own "country supper" closeness to News International, as revealed in such detail at the Leveson Inquiry. Mr Cameron has considerable charm and fluency. But both he and, by extension, his Government show an alarming tendency not to think things through.