Sue Ferns senior deputy general secretary of Prospect, the main union in National Grid, said: “The gas deficit announced by National Grid today demonstrates why the government needs to radically reassess UK energy policy.

"Our current reliance on the privatised market, and failure to properly plan ahead, leaves us in a costly scramble to fill supply shortfalls.

“At the same time, our increasing reliance on foreign energy sources makes us more vulnerable to sudden shocks, such as this week’s severe weather.

“The government must prioritise investing in new infrastructure to future proof the UK’s energy supply and to ensure that the UK can cope with unexpected events.

"There are important questions that need to be asked about future resilience when there are severe weather conditions particularly when flexible and responsive supply, currently provided by coal, is no longer available."