They also point to falling output from coal, gas and nuclear power stations due to closures – leaving the country more exposed to intermittent renewables such as wind and solar farms.
Tom Greatrex, chief executive of the Nuclear Industry Association, said: “We shouldn’t have to rely on other countries to keep the lights on, and we certainly shouldn’t leave our energy future up to their decisions.
“We desperately need more baseload power, so we need to get on with a full new nuclear programme.
“That way, Britain gets the jobs, the energy and the investment, and not just the bill.”
He called for the Government to push ahead with a final investment decision on the proposed Sizewell C nuclear power plant in Suffolk, as well as work on a proposed plant in Wylfa, Anglesey.
The only new nuclear power station currently under construction is Hinkley Point C – with all of the UK’s existing sites set to come offline this decade apart from Sizewell B in Suffolk.
Following nuclear closures and the end of coal-fired generation last month, the electricity grid now relies on gas-fired power stations, a growing share of wind and solar power, biomass and interconnectors, as well as some hydropower and pumped storage.
This winter Neso will rely on interconnectors to supply roughly 11pc of the nation’s available power during a cold spell when demand will be at its highest.
That is up from about 4pc in 2019.
In the past three years, interconnector capacity has grown to 10.5 gigawatts after the opening of the 1-gigawatt ElecLink with France and the 1.5-gigawatt Viking Link to Denmark.
A third link, the 500 megawatt Greenlink cable to Ireland, is expected to open at the end of this year.
Net exporter ambition
Neso has said that it expected interconnectors with Europe “to play an important role in helping maintain secure supplies” of electricity to Britain, while also providing useful flexibility.
The grid operator can intervene if power is flowing in the wrong direction during a crisis.
For example, it was forced to step in earlier this month when low wind output and higher-than-expected demand left the system facing a potential shortfall on October 14.
However, Kathryn Porter, an independent energy consultant at Watt Logic, said some interconnectors had provided patchy availability in recent years and European countries may be less willing to export if their own supplies are stretched.
From 2021 to early 2023, one of the UK’s links with France was operating at reduced capacity after suffering damage from a fire.
Ofgem, the energy regulator, has recently indicated it is against further interconnectors being brought online.
The watchdog has suggested that it wanted to block the construction of new cables — which could take capacity to as much as 20 gigawatts in the next decade — because they risk benefiting power producers more than consumers.
Countries that have the ability to export their unused power tend to see prices rise due to demand from abroad, Ofgem found.
Under the Government’s plans to reach a “net zero” power system in the 2030s, ministers want Britain to become a net exporter of power.
“Not only might the imports we want not be available in the future, but Ofgem has also declined almost all future proposed interconnector projects,” Ms Porter said.
“So when Neso says it expects to have more capacity in future, where is that going to come from?”
On Friday, a spokesman for the Department for Energy Security and Net Zero said: “We are committed to boosting Britain’s energy security.
“Our mission is for clean power by 2030 because this is the best way to achieve energy independence, protect bill payers and reduce imports.
“We only import from international partners when energy is cheaper in Europe, so families pay lower prices for their energy.”
The UK’s record 26.3 terawatt hours this year was comprised of 34.5 terawatt hours of imports and just 8.2 terawatt hours of exports.