Alistair Darling cannot do attack politics. When he tries, it is painful to watch. He’s about as scary as a sleeping cocker spaniel. He does not do angry. Mildly irritated, perhaps. Actually, make that a tiny bit miffed. It must drive Mrs Darling crazy, as it would be like fighting with a cotton ball.

This does not stop him from trying, of course. He attempted to go on the attack yesterday at Treasury Questions as MPs repeatedly asked for details of the 10p rescue package. The result was less than impressive. The cotton ball was on the rampage. The result? Quite a lot of fluff.

The Shadow Chancellor George Osborne was in full scorpion mode. “What is becoming clear is that this incompetent Government can’t even organise a humiliating U-turn without messing it up.”

Mr Darling blinked in his mildly startled way. He’d been under pressure for the entire session to confirm that the rescue package would be backdated to April 1. He’d refused to say the word “backdate”, I know not why. Maybe he had a bet with Mrs Darling. Maybe it’s not true. But he would not be cajoled into it.

The Scorpion taunted him. The night before, in the Newsnightstudio, the Chief Secretary to the Treasury, Yvette Cooper, had refused to say whether the package would be backdated. But then rebel leader Frank Field (the Che of the Commons) insisted that the PM had told him it would be backdated. So was Frank or Yvette right?

At this challenge, Mr Darling’s caterpillar eyebrows stirred and he felt something coursing through his veins. He examined it and found that it appeared to be an emotion, the strongest he’d ever experienced. Finally he identified it as mild irritation. “I’d say this to you,” he began, “your position on this . . . ”

“Answer!” demanded Tory MPs. That’s all it took to derail the cotton ball attack. Mr Darling began to babble about the Tories changing their position (which seemed a bit rich) and then embarked on the journey that is his explanation. It was all about his letter on the plan. He did not use the word “backdate”. Instead, he said: “Our focus is to ensure that we allow the average losses from the abolition of the 10p band to be offset for this year.”

Mr Osborne snapped. “No one is interested in the letter,” he said. Would the plan be backdated? Yes or no?

The answer was 184 words long, none of which was “yes”, “no” or “backdate”. Yvette Cooper, next to Mr Darling, looked exhausted. Labour MPs clearly wished to be elsewhere. As ever in politics, the devil is in the detail and, in this case, the detail is a real devil.

The cotton ball fluffed on, muffling clarity even further. Mark Harper, a Conservative, tried again: “Is it not obvious that the Prime Minister has done a deal to buy off Labour MPs next Monday, and that the Chancellor is in the process of reneging? Labour will find they have been conned.”

At this the eyebrows jumped, for Mr Darling was feeling that emotion again. But this time it was even stronger. The medium irritation was overwhelming. Before he could stop himself his mouth opened. “Absolute nonsense!” he cried. He tried to attack the Tories again before slumping on the bench. My but this emotion stuff was draining. It was time for a lie-down.

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