Drivers at P&O Trans European, who deliver petrol and fuel supplies on contract to Shell, announced on Wednesday they would be staging the strike after rejecting a 2.5% pay rise.

If the industrial action goes ahead, supplies to Shell filling stations across the UK will be disrupted.

But on Thursday, P&O said following talks with the Transport and General Workers' Union (T&G), it had doubled its pay increase to 4.5%.

Dangerous job

A spokesman for the company said: "It has been agreed that T&G will put the company's revised offer of a 4.5% pay increase to its members with a recommendation to accept."

Negotiations between the company and the union have been taking place since January in an attempt to find a settlement.

Last week, 294 drivers on the Shell Main Fuels contract voted overwhelmingly in favour of strike action out of a total number of 394 who were balloted.

The drivers want a substantial pay rise to reflect what they say is the dangerous and responsible nature of their job.

Ron Webb, T&G national secretary, said: "Union members at P&O have suffered for years with low pay increases.

"Average industry wages are good, P&O and Shell report huge profits, so why are they so reluctant to pay our members fair wages?"

'Acceptable agreement'

The strike is due to be held from 19 July to 22 July.

On Wednesday, Shell said it was "working closely" with P&O and the T&G to reach an agreement that was "fair and acceptable" for all parties.

Shell operates 1,100 petrol stations across the UK.

The walkout involves staff from 13 fuel depots at Buncefield in Hemel Hempstead, Hertfordshire; Shell Haven at Thurrock, Essex; Avonmouth in Bristol; Plymouth; Hythe in Southampton; Haverfordwest; Killinghome and Kingsbury in the Midlands; Stanlow in Cheshire; Grangemouth; Aberdeen and Inverness.