David Cameron appears to be getting himself into all sorts of trouble over tax avoidance.

Earlier this week the PM criticised Jimmy Carr when he was questioned on the comedian's tax affairs, which according to an investigation in The Times have seen the celebrity use an avoidance scheme to cut most of his tax bill.

It's always dangerous for politicians to make moral judgements (remember John Major's 'back to basics'). So perhaps Cameron was just tired when he lashed out at Carr, or maybe because the comedian has attacked tax avoidance in sketches the PM thought he was an easy target.

That's not the case with Take That's Gary Barlow though, darling of the Diamond Jubilee, about whom Cameron was asked in a press conference in front of a rather bemused Aung San Suu Kyi earlier.

Barlow and other members of his band have also been found to use avoidance schemes by The Times' investigation.

But this time Cameron was coyer – he said he wasn't going to give a 'running commentary', but had commented on Carr's case because it seemed 'particularly egregious'.

Does that mean when he refuses to comment on future tax avoidance stories that come out, it is because they are not serious enough?

He then said it was OK for people to arrange their tax affairs, but not for them to avoid tax – the lines in his argument are fuzzing up by the second.

In fact the PM is getting dangerously close to the mistake Ed Miliband made when he started talking about a division between good businesses and bad businesses.

Surely a clever leader wouldn't get into such contortions over an issue that could involve many people connected to his party.

Surely a clever leader would play to his party's hearts by, say, bringing back tougher exams for schools like O-levels. Why didn't the PM think of that?