British authorities could run out of salt to grit roads within three or four days as Britain faces a week of paralysis after the heaviest snow for at least 18 years, it has emerged.

Forecasters expect blizzards to return to the South throughout Tuesday, with sleet and snow continuing at least until the end of the week but stocks of salt are already nearly depleted in some councils.

One in five workers took a “snow day” on Monday as the weather shut 2,800 schools and brought chaos to the road, rail and bus networks. Supermarkets saw a rush from shoppers buying ready meals, soups and porridge amid fears that supply lines could be affected.

Severe weather warnings have been issued for much of Scotland and North-East England and there was a high risk of “extreme weather” throughout the rest of the country.

Town halls stockpile relatively low levels of salt, anticipating only seven or eight days of mild snow and ice per year. With the sub-zero temperatures already experienced this winter and heavy snow over the past 24 hours some councils have used up much of their stock.

Paul Bettison, chairman of the environmental board at the Local Government Association, said that England could run out of gritting salt within two weeks with a big freeze although individual authorities might run out earlier.

With more than 15cm of snow falling since the weekend, many councils have already gritted four or five times as the salt loses its effect if temperatures fall below minus 4C or if there are heavy snowfalls after gritting.

“If we had a freeze lasting more than two weeks the country might run short of salt,” Mr Bettison said. “But many councils may be on the phone after four days asking for more. Those with better stockpiles should be able to help out the others,” he added. He said that if salt ran out it would have to be shipped in from Europe.

The last time Britain experienced such widespread snowfall was in February 1991. The Met Office said that up to 1ft (30cm) of snow could fall in London while northern England and the Pennines could see as much as 20in (50cm).

Tags: snow, weather, winter