"George Osborne was pretty specific at the Times fringe meeting today that he doesn't see this as the Conservatives' 'Clause Four moment', but clearly he and David Cameron are using this now as a totem of their refusal to be rushed into populist measures before they are ready.

"There's an element of bluff in it all, I think, because even if they do intend to offer tax cuts before the next election the last thing they could do would be to offer them now. And Osborne makes the point that they won't be able to see the books until they get in and see whether they can afford it.

"Their great worry, of course, is that Gordon Brown becomes Prime Minister, having had access to the books for the last umpteen years and has his own tax cut before the next general election, which they would feel they have to match on the spot.

"I think they deliberately sought a battle on this subject and they will be pretty pleased that the likes of Norman Tebbit and Edward Leigh - pretty predictable figures - have emerged to attack this.

"Cameron needs to be seen taking on the party and this is a pretty safe one for him because they're not actually ruling out for all time, they're just saying they won't be committed to tax cuts at the moment. So it's a battle that shows Cameron is taking on his party and winning

"The tactics are similar in a sense to those employed by Neil Kinnock when he took on the Labour Left in the 1980s over the EU or unilateral disarmament, then Tony Blair did the same.

"The 'Clause Four moment' then was proof that the Labour Party had changed - I don't think this is quite as dramatic as that, especially if they do end up offering tax cuts, but it's a similarly symbolic battle that they know they can't afford to lose."

Times Recommends

• Please help: maimed children of war want their lives back
• Unlocking the cruellest prison
• Prince Charles named in £81m court battle