The UK’s power supplies could be down by mid July, the government has said.
The National Grid has said the “short-term” forecast for blackouts in the UK will be less than the level of the peak demand of the month of June.
It will be the first time in history that a country has had a peak demand, when demand is in excess of demand.
The forecast was issued on Wednesday morning, before a meeting of the National Grid Group.
The warning comes as the UK government faces pressure from the Opposition to use the Autumn Statement as a chance to increase the country’s electricity output, which has been stagnant in recent years.
A second meeting of that group will take place on Wednesday.
It is understood the government will say more on Wednesday about its plans for the next couple of months.
The UK is currently facing a “red alert” condition, meaning that electricity supplies could become dangerously low for a period of time if the demand is not significantly reduced.
This condition will come into effect on 1 July, with a reduction of up to 3 per cent of power supplied to homes and businesses.
The last time this happened was in the late 1980s.
UK Power Networks says the forecast is the “worst” it has ever seen, and the first since the 2008 crisis.
It says that while the peak of demand for electricity is now “well below” the peak it experienced in the last crisis, “there is no guarantee that the current situation will remain the same”.
The outlook is similar to the previous two forecasts, released on 1 June and 23 May, but the outlook for supply has not changed much.
It said it is possible for supply to be down for as long as the peak, but that it would be less likely if the current demand is less than it was in 2012.
BBC Weather’s Andrew Brown has been reporting from London, where there has been a spike in the number of severe weather events.
He has been following the situation with keen interest.
He said the government was likely to announce plans to cut electricity to about one million homes, while businesses would see their power supplies cut off.
In total, more than a million homes will be affected.
The government has promised to “take measures to protect” homes and people in the capital from blackouts.
It has promised “extraordinary measures” to protect the UK economy.
The British Medical Association is also warning of the potential for further cuts.
A number of doctors have already quit their posts.
BBC News: Sarah Houghton