Travel chaos is set to continue on Monday with freezing conditions and heavy snow causing flight cancellations and delays at Britain's busiest airports.

Passengers hoping for a Christmas getaway have found themselves stranded at airports, with hundreds of people camping out in terminals for another night after planes were grounded.

Temperatures plunged overnight, with a record low for Northern Ireland seen in Castlederg, County Tyrone, where the mercury plunged to minus 18C.

The lowest UK temperature overnight was thought to be minus 19.6C, recorded in Chesham, Buckinghamshire.

Forecasters have said the UK is experiencing some of the most severe winter weather in a century, with continued sub-zero temperatures and snowfalls of up to 20cm expected on Monday.

Motoring organisations have warned of "potentially fatal" conditions on the roads as commuters struggle into work, with others hoping to make an early start to their Christmas holidays.

On the London Underground, there were severe delays on the Metropolitan line which extends as far as Chesham and Amersham in Buckinghamshire. There were minor delays on some other Tube lines.

Those stuck at Heathrow would have felt bitterly cold temperatures of minus 9.4C overnight.

A British Airways spokesman said he did not yet know how many flights would be leaving. He said: "Most of our aircraft are still frozen. With incredibly low temperatures at Heathrow, it's difficult to get anything moving."

Shadow chancellor Alan Johnson hit out at the Government's handling of the situation, saying people felt they had been told to "get a shovel or stay at home". Transport Secretary Philip Hammond defended his approach, saying he had been consulting with the Government's chief scientific office about the need for major long-term investment.

Aisling Creevey, a forecaster with MeteoGroup, the weather division of the Press Association, said: "There are temperatures of minus 14 and minus 15 quite widely across the UK, with no let-up in sight. We will be seeing figures like this over the next night or two, with significant snowfalls forecast for Wednesday."

Those hoping for a white Christmas may be disappointed however - with the weather for Christmas Day itself set to be "wet and windy", she said.