IT is right that tough decisions have to be taken to tackle the deficit and it is right that we all have to make a contribution to filling that enormous black hole.

But there is a glaring flaw in the coalition's plan to cut child benefit that simply hasn't been thought through and now leaves David Cameron with a dilemma.

How can it be right to tell families in which there is one person earning more than £43,875 a year that they will lose out on child benefit, while those with two earners on a joint income of £87,000 go untouched?

Someone with only a very basic understanding of maths, let alone a Chancellor, would see that it is plainly unfair.

In view of the uproar such an illogical step has caused, Mr Cameron's sudden revival of tax breaks for married couples was looking suspiciously like a damage limitation exercise last night.

If it is intended to compensate those who are to lose out on child benefit, it will fly in the face of the Conservatives' manifesto pledge not to hand tax cuts to higher-rate taxpayers.

And what's more, experts are warning that the marriage tax break plan could end up costing £5bn - £4bn more than the estimated child benefit savings.

When pressed for further detail, the Prime Minister requested to be allowed to announce "one policy at a time".

In other words, he has a lot of thinking to do about how to unravel the knots in which he has been tied by an ill-considered and unfair announcement on child benefit.