In October National Grid ESO, which balances electricity supply and demand, said that Britain faces a greater risk of blackouts this winter than last given the availability of supplies. 

It has forecast a capacity margin – the buffer of spare electricity supply – of 6.6pc, the lowest since 2016.

The dormant power stations’ backers argue that restarting them could provide an extra source of electricity to help meet demand.

They claim they could also help cool prices: first, by dampening the scarcity effect where suppliers capitalise on demand by putting up their prices.

Secondly, they say the plants’ size means that Severn in particular could end up setting prices in the market instead of less efficient equivalents currently doing so. 

Directors argue that this effect could help shave £2.1bn off wholesale power prices during the first three months of the year, which would likely lead to lower household bills. Whitehall sources said they did not recognise this figure. 

In a report for the directors, energy market analysts Cornwall Insight forecasts average wholesale prices of £209.99 per MWh during the first quarter of 2022 if the stations are in the market. The forecast is £10.35 per MWh lower than a base forecast of £220.33 per MWh without them.

Tom Edwards, senior modeller at Cornwall Insight, said: “If you bought these plants back, especially Severn because it’s more efficient, I think the [wholesale] price would fall. 

“By how much it falls will depend on behavior, wind speeds, and what happens on the continent.”

Cornwall estimates total notional profits – known as the spark spread-  of £96.7m for the plants during the first quarter of 2022. 

The directors have also argued that generators should be able to get greater certainty over revenues in the electricity market, and should be given stricter penalties if they do not fulfil commitments.

A Whitehall source insisted there was nothing to stop the owners re-starting the plants outside of the capacity market, adding that “if the stations are as competitive as they maintain, they could enter the market without government support.”

The source added: “A bespoke arrangement would undermine the existing legal and regulatory framework. In future, we might expect market participants to stop entering the capacity market and wait until the winter and then try to hold Government over a barrel – thereby undermining the whole process we have for providing security of supply.”

A BEIS spokesman said: “We have sufficient capacity to meet demand this winter. It is neither necessary nor appropriate for Government to enter into bespoke contractual arrangements for the return of Severn and Sutton Bridge, or any other generators, to provide electricity capacity this winter.”