Fuel tanker drivers have rejected a proposed deal aimed at averting industrial action, raising fresh threats of strikes which would cripple petrol supplies.

Around 60 Unite officials overwhelmingly turned down a deal which was thrashed out during six days of talks between the union and representatives of six fuel distribution companies.

The union urged motorists not to panic buy and stressed that it had not yet decided whether to name any strike dates. The union only has until Friday to call a strike and will have to give seven days' notice of industrial action.

It is believed that progress was made on a number of issues including pensions, health and safety and training. Diana Holland, assistant general secretary of Unite, said: "While there has been some progress it is clear that our members need more guarantees and assurances from the employers about their commitment to meaningful minimum standards. We remain committed to achieving a negotiated settlement that brings stability and security to a vital industry and gives this workforce, and the public, confidence that the race to the bottom is ending."

Ms Holland accused operators of presiding over an "undercutting" and "erosion" of standards covering issues such as health and safety and pensions.

Unite officials have contacted the conciliation service Acas and said they hoped employers would agree to hold fresh talks in the coming days. Peter Harwood, Acas chief conciliator, said: "Naturally, we are disappointed at today's outcome, following the parties' intensive talks at Acas over the last two weeks. We are contacting the parties and the challenge now is to see if we can find a way forward."

After the row flared last month the Government advised motorists to top up their cars with petrol and to store fuel in jerry cans, leading to panic buying and shortages of supplies. There were chaotic scenes at garages as long queues built up, leading to criticism of the Government for the way they had handled the dispute.

Energy and Climate Change Secretary Edward Davey said: "We are disappointed that an agreement has yet to be reached. We understand that these are complex issues but urge both parties to work towards a negotiated resolution with the support of Acas. The Government continues to believe that any strike action would be wrong and unnecessary."

A spokesman for Hoyer, one of the firms involved, said: "The decision by Unite to reject the proposals agreed between employers and the union after six days of constructive dialogue through Acas is a serious blow. The team from Hoyer, along with other key industry employers, engaged fully and professionally in these talks and remain open to negotiation with a view to achieving a positive resolution to this dispute and avoid the possibility of any damaging strike action by Unite. Having reached this point, Hoyer will now reflect on all available options.

"However, we have made comprehensive contingencies as a business and we remain committed to ensuring that despite any strike action by Unite, we make every effort, together with the armed forces, to maintain fuel supplies to a level that keeps disruption to business and the general public to an absolute minimum."