The Government’s “reasonable worst-case scenario” plan shows that Britain could face an electricity capacity shortfall totalling about a sixth of peak demand.
The shortage would occur even after emergency coal plants have been fired up, according to people familiar with the government’s planning.
This would mean the UK could be forced to endure organised blackouts for industry and even households.
Under the plans, below-average temperatures and reduced electricity imports from Norway could leave the UK four days when the country may need to trigger emergency measures to conserve gas.
Earlier this week, fears of winter fuel rationing were exacerbated when Norway threatened to limit its exports to the UK and Europe this winter.
The Norwegian government also announced new rules limiting the sale of power to foreign countries earlier today.
This comes as the country’s hydroelectric power plants – which generate the majority of its energy – are being threatened by unusually hot and dry weather.
The announcement comes amid growing anger in Norway over rising domestic energy prices.
The UK is expected to be more dependent than ever on the Continent for power this winter.
The National Grid expects the UK to be able to draw on 5.7 gigawatts of power from Europe – equal to around 10 percent of demand at peak times.
But around a quarter of this figure, 1.4gigawatts, is expected to come from Norway.
Kathryn Porter, an energy consultant at Watt-Logic, said the newly proposed measures “put at risk the ability of Britain to import from Norway this winter”.
She added: “National Grid ESO needs to urgently update its winter outlook taking account of this threat to Britain’s energy security.
“Longer term, we need to develop more domestic generation and rely less on imports.”