The Conservatives have branded Chancellor Gordon Brown a "highway robber" for increasing petrol duties in a publicity campaign.

They have unveiled posters of Mr Brown brandishing a petrol pump, with the slogan: "Labour's Highway Robbery. 72p in every £1 of petrol is tax. Is this what you voted for?"

The month-long campaign will target petrol station forecourts as the Tories estimate 63% of the population buy petrol.

They will book advertising space on garage forecourts, and distribute stickers and cardboard cut-out of the Chancellor to local constituency associations.

The campaign will start on 29 July, the first Saturday of most school holidays, when thousands of motorists will be filling their cars for long journeys.

The Tories have chosen a popular issue for their attack.

Growing anger

The government has faced growing public fury over petrol prices, with some garages selling four-star at more than £1 a litre.

Last week, a survey for Channel 4's Powerhouse found that 62% of the British public thought duty on petrol should be cut by 10p a litre, even if it meant income tax rises, cuts in public services or the introduction of motorway tolls.

Just 23% of the 1,000 people questioned thought that fuel duty should not be reduced.