Chancellor Alistair Darling's first Budget is expected to be the toughest since Labour came to power more than a decade ago.

An escalating national deficit makes tax cuts or spending boosts almost impossible and the forecasts are for a round of increases in "green" taxes on motoring and flying.

He is widely expected to increase the proportion of revenue from green taxes, slapping a "showroom tax" of as much as £2,000 on gas-guzzling 4X4 vehicles, as well as transforming air passenger duty into a tax on flights in a bid to cut carbon dioxide emissions.

But he is coming under mounting pressure from the motoring lobby to scrap a planned 2p rise in fuel duty due to come into effect on April 1, with reports today suggesting that he may make a last-minute decision to put it off until the autumn.

Describing it as the "2p or not 2p Budget", AA president Edmund King argued that the Chancellor should at least defer the increase, which was pencilled in last year at a time when a barrel of oil was less than two-thirds its current price of $107.

"Fuel price instability is damaging to people and the economy and while this is largely influenced by the market, we believe the Government can do more to help people and business weather the financial damage and uncertainty high prices cause," said Mr King.

David Frost, director general of the British Chambers of Commerce, said: "The Treasury has had a windfall from the rising price of oil of £2.2 billion since last October.

"The Chancellor should recognise the increasing costs being incurred by business because of rocketing oil prices and scrap the planned 2p rise in April."

While the Government makes great play of the use of tax levers to encourage environmentally-friendly behaviour, Mr Darling will be aware that he risks a public backlash if pump prices - already well over £1 a litre - are pushed up further.

An eve-of-Budget poll by YouGov, for accountants BDO Stoy Hayward, suggested that 59 per cent of voters believe "green taxes" are designed mainly to fill Treasury coffers rather than protect the environment.

© Independent Television News Limited 2009. All rights reserved.