Last-minute talks are being held to avert strikes that could disrupt fuel supplies across Britain.
Around 500 workers contracted to deliver Shell's fuel supplies around Britain are due to walk out from 6am on Friday until 6am the following Tuesday in a dispute over pay.
If their walkout goes ahead, it will affect one in 10 filling stations across the UK.
The drivers work for Hoyer UK and Suckling Transport. They are demanding a pay rise from their current basic wage of £32,000 a year, saying that it has not increased since 1992. Unions are demanding basic pay of £36,000.
Drivers have rejected an improved offer of a 6.8% pay rise, which the companies claim would have increased drivers' average salaries, including overtime, from £36,500 to around £39,000 a year.
Meanwhile, the Government has already urged motorists not to panic-buy fuel because of fears of petrol shortages.
A spokesperson for Prime Minister Gordon Brown said contingency plans were in place to minimise disruption.
He said: 'We want the public to continue to buy as normal to avoid creating problems that might otherwise not exist.'
Even so, the Government said some petrol stations could run out of fuel.
Shell is understood to have a team working to minimise any disruption by maximising stocks of fuel and prioritising deliveries.
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