Temperatures in Britain plunged to minus 21C as the country suffered its coldest night of the winter so far.

The mercury sank to minus 21.2C (minus 6.2F) in parts of the Scottish Highlands - considerably colder than some home freezers - with bitterly cold temperatures everywhere else on another day of widespread weather disruption.

Icy conditions have again left roads in a treacherous state and caused delays and cancellations for rail and air passengers. Hundreds of schools have also shut again, resulting in a full week of closure for some children.

The relentless cold weather has brought more havoc with dozens of big companies having their gas rationed after domestic demand soared to record levels and warnings that many grit stocks were reaching crisis point.

Manchester and parts of the Brecon Beacons in Wales saw temperatures fall to minus 15C (5F), with Glasgow reaching minus 8C (18F), Cardiff minus 5C (23F) and London hovering just below zero (32F).

There will be little respite during the day, with more snow for eastern England and temperatures likely to be pegged at or below freezing in all parts. The wintry conditions are also expected to last well into next week as the coldest spell for more than 30 years grinds on.

Gareth Harvey, from MeteoGroup, the weather division of the Press Association, said: "There is no change in the weather pattern - it is very cold and icy again. During the daytime just about everywhere is going to be zero or below apart from a few coastal areas."

The latest round of school closures have taken place in Salford, Northumberland and Gloucestershire, with hundreds of others shutting in Hampshire, Buckinghamshire and Hertfordshire, and there is mounting anger on behalf of parents at the extent of the shutdowns, with criticism that many have been unnecessary.

The death toll caused by the big freeze rose again yesterday after the body of 45-year-old Philip Hughes from Slough was recovered from beneath the ice in a frozen lake in Frimley Green, Surrey. At least 22 people have died since before Christmas in incidents thought to have been related to the weather.

On the roads, drivers face more hazardous conditions as people struggle to get to work and the shops and some councils have been forced to ration their salt as one of the biggest suppliers of rock salt in the UK asked the Department for Transport to draw up a list of priority customers.