Andrew Grice: David Cameron may live to regret speaking out about Jimmy Carr's tax

At the very moment that Downing Street was telling journalists in London that the Government did not normally comment on the tax affairs of individuals, David Cameron had other ideas 5,550 miles away in Mexico City. Interviewed by ITV News on the last day of a three-day visit, the Prime Minister was asked about reports back in Britain that the comedian Jimmy Carr had sheltered £3.3m a year from tax through a Jersey-based avoidance scheme.

Mr Cameron had read the reports on his iPad and decided not to pull his punches. He said some such schemes "are frankly morally wrong", accusing the comedian of putting money raised from his hard-working, tax-paying fans into some "very dodgy tax avoiding schemes".

Good populist stuff, especially in hard economic times. But some Conservative MPs think Mr Cameron was unwise to jump on the tax avoidance bandwagon. "Sometimes it is better to think before you leap," one said. Yesterday, Mr Cameron was inevitably asked his views on Gary Barlow of Take That, who is reported to take advantage of similar tax shelters. This was a bit closer to home since Barlow was awarded the OBE only last week.

The questions were batted away, but they won't go away. Mr Cameron reverted to the Government's traditional line on people's tax affairs, insisting Carr was "an exception" because his details had been published. Similarly, Number 10 sought to draw a line between "aggressive" and more routine tax avoidance. Tricky, and the questions kept coming: journalists wondered whether Mr Cameron had condemned Carr because he is a "Labour celebrity" but is coy about Barlow because he is a Tory one.

The proverbial genie is out of the bottle and the media will not stop asking Mr Cameron his views about other celebrities, Tory party donors and businessmen who advise the Government.

His surprising remarks have also revived the media's interest in whether the tax returns of senior Cabinet ministers would be published. Mr Cameron said in April he was relaxed about that but the issue has gone quiet since.

Number 10 insists the matter is still under consideration but it might have been kicked safely into the long grass if the PM had not waded into the row over Carr. Why did he break with convention? Downing Street's private polling shows that the public's number one concern about the Government is that it is "out of touch". This is very dangerous for Mr Cameron because the evidence given to the Leveson inquiry has reminded people about his "country supper" lifestyle and well-heeled background.

If you asked voters what the Government had done on tax, the chances are they would say it had cut the 50p top rate for the rich rather than the Coalition's preferred answer – raising tax thresholds at the bottom. Perhaps this was another reason why Mr Cameron played hardball on tax avoidance. He may come to regret his intervention – and the decision to cut the tax on incomes over £150,000 a year when millions of ordinary people feel so squeezed.