The cost of keeping the county's roads gritted during the recent snowy weather has cost taxpayers an extra £500,000, it was revealed today.

The heaviest snowfalls for 20 years has meant running services day and night, causing County Hall to exceed its annual winter maintenance budget of £1.5 million.

Staff working 24 hours a day to treat roads and pathways, buying fuel for gritting trucks, buying extra salt and paying farmers to treat roads, has caused costs to spiral.

Matthew Lugg, director of highways and transportation at County Hall, said: "We are predicting an overspend of £500,000, but it could be even higher than that.

"There have been cost implications, but the roads will be safe."

The council has also been forced to buy a version of household table salt to treat roads for the next two weeks because it feared running out of the salt it usually uses in grit.

The new salt is being mixed with sand and then spread on roads as an alternative to regular grit, which many councils have run out of this week.

Mr Lugg said: "We were struggling for supplies as our usual suppliers were telling us we may not be able to get any more in. We were faced with a potentially catastrophic situation."

Council bosses in the city, however, say they are not facing the same budget pressures.

A spokesman said: "We have annual budget of approximately £200,000 for winter road maintenance, and are still within that budget."

Meanwhile, county council drivers have complained they are being overworked and that the new salt is causing major problems with equipment.

One, who wished to remain anonymous, told the Mercury: "The new stuff is no good. It's too thin and freezes.

"It's clogging up the machines and turns into sludge. It's making our routes take twice as long to complete because we have to keep getting out of the lorries and unblocking the pipes.

"We're all fed up. We're supposed to work 14 nights in a row, but we're now being told it will be more than that.

"The fire service and ambulance have relief crews. There are only 17 of us and we're all working at the same time."

In response, Mr Lugg called the current situation "exceptional" and called on his drivers to keep working through the bad weather.

He said: "The gritters have had a very tough fortnight and things have been difficult – but that's life."

He admitted some gritting lorries had broken down last week, but said it was not as a result of the new salt being used.

The money to cover the overspend will come from reserves, but today councillors called for reassurances after it was revealed the county council planned to make savings of £215,000 in next year's winter maintenance budget – which covers gritting.

County councillor Bill Boulter said: "Climate change theory suggests that we will experience more extreme weather changes.

"I am concerned that this winter maintenance budget leaves us ill prepared for another severe spell of severe snow and ice."