The union says its members deserve the extra pay
Talks aimed at halting a strike by drivers who deliver fuel to Shell petrol stations have broken down.
The Unite union rejected an offer by the drivers' employers, Hoyer UK and Suckling Transport, to up pay by 6.8%.
Unite says it does not meet its demand for minimum pay of £36,000 a year. Hoyer said staff earned more than that.
Unite has said 641 drivers will go on strike for four days from 13 June but added it was willing to hold talks with managers at conciliation service Acas.
The union said it had already won a mandate from its members to take industrial action.
Hoyer's Bernie Holloway called Unite's decision to reject their improved pay offer "a great disappointment".
"We believe this is a very good offer, and combines with previous pay awards to produce an overall increase in average earnings over the last four years totalling 27% - double the rate of inflation," he said.
"However the union have responded by re-enforcing their demand for a 13% increase."
He said the firms would continue to "explore all possible options to resolve what is clearly a very difficult situation".
Hoyer UK, which is leading the negotiations, argues the drivers already earn more than £36,000 in average pay, and this would rise to about £38,500 with the wage increase.
But Unite argue that the drivers earned £32,000 for working a basic 48-hour week - about the same as they did 15 years ago in real terms not adjusting for inflation.
Officials say Hoyer UK is most likely factoring in overtime into their figures, which the union is not.
"Our members' dedication helps Shell make vast profits," said Unite national officer Ron Webb.
"All they are asking for in return is a living wage - one that reflects their skills, their heavy working week and helps make ends meet at a time when every worker in the country is being hit hard by rising fuel and food prices."
In January, Shell reported annual profits of £14.2bn for 2007, a record for a UK-listed company, helped by the surge in oil prices.
Record oil prices have had a knock-on effect on petrol prices.
In the UK, average prices for unleaded petrol have now reached 112.6p per litre and diesel prices have risen to 124.2p, according to figures calculated in May by the AA.