Why David Cameron fears the fuel duty time-bomb

Traditionally, the Budget is a jealously guarded state secret. One Chancellor - Hugh Dalton in 1947 - was forced to resign when he whispered the contents of his Budget box to Lobby journalist John Carvel.

But these are desperate times, and David Cameron fears that, unless he calms down the natives, he could have a Cairo-style revolt on his hands in Parliament Square. Which is why he has dropped an unusually heavy pre-Budget hint that the rise in duty on the price of petrol and diesel - of 1p plus the Retail Price Index - could be dropped

The RPI-plus formula was put in train by Alistair Darling when he was still Labour Chancellor to deal with climate change, and it is now regarded in Downing Street as a ticking time-bomb due to go off under the coalition in April.

The price of fuel at the pumps has already rocketed from £1.19 a litre in November to £1.30 a litre now, and the unrest in the Middle East is threatening to drive the price up even higher.

The index-plus-1p formula could add around 5p per litre to the £1.30 pump price. That could herald the return of the sort of fuel protests which so nearly brought the Blair government to its knees.

Yesterday began with the Camerons suffering the indignity of a knock on the door of Number Ten by slick-haired Quentin Wilson - the motoring pundit who pre-dated Jeremy Clarkson as the presenter of Top Gear - handing in a protest petition on behalf of the FairFuel UK campaign.

It is easy to imagine Sam Cam telling her husband to "do anything to get rid of that man".

It's not that simple, however. Their nextdoor neighbour, Chancellor George Osborne, is happy to talk about removing Labour's 1p duty increase, but is not so keen on stopping the normal RPI rise in fuel duty going ahead. If Osborne gets his way, he will announce that the duty will rise in line with inflation. That would still put around 4p on the price of fuel, leaving motorists hopping mad.

The Mole hears that the memos have been flying between Cameron and Osborne's offices about the pending fuel rise. Cameron used Prime Minister's Questions yesterday to put pressure on his Chancellor by announcing that the Treasury's coffers – despite the recession – have been boosted by an increase in receipts from the existing fuel duty, bloated by the general rise in oil prices.

"We will look at the fact that extra revenue comes to the Treasury when there is a higher oil price and see if we can share some of the benefits of that with the motorists," said Cameron.

Cameron was clearly giving a nudge to Osborne that the Treasury can actually afford to be generous in cutting the Labour duty rise and indexation for this year, without having to increase taxes elsewhere to pay for it.

Cameron's heavy hint at the dropping of part if not all of the fuel duty increase is further clear evidence that the new Masters of Spin – Andrew Cooper and Craig Oliver – are having their effect. They concluded that the fiasco over the plan to sell the forests was largely due to a failure to prepare public opinion, which they call "rolling the pitch".

Now Cameron and his Cabinet are busier rolling the pitch than the groundsmen at Lord's. In addition to the PM's use of the heavy roller, Home Secretary Theresa May has signalled that next week's long-awaited report on 'old fashioned practices' in the police force will herald cuts in overtime allowances, housing and travel expenses, and redundancy pay-outs for coppers' bad backs. ·