National Grid has warned that its capacity to supply electricity this winter will be at a seven-year low.
It said this was due to generator closures and breakdowns.
However, both the electricity infrastructure operator and the Government insisted there was no danger of any blackouts in the event of unexpected scenarios, such as an extremely cold winter.
Energy minister Matthew Hancock said: “We are absolutely clear we are taking the measures necessary in order to have secure energy supplies this winter.”
Cordi O’Hara, National Grid’s director of market operations, said: “It’s clear the country has the ability to meet its energy needs in a cold winter. But we cannot be complacent and will be monitoring the situation right through to spring next year.
“The electricity margin has decreased compared to recent years, but the outlook remains manageable and well within the reliability standard set by government.”
Spare electricity capacity, which ran at about 5% over the winter months last year, would be nearer 4% this year, National Grid said. Three years ago the margin was 17%.
The network operator said it is finalising contracts with three UK power stations to provide reserve power in case of higher-than-expected demand.
In the event of disruption of Russian gas supplies to Europe, National Grid said more expensive gas could be imported. This would only happen in the “most extreme scenario”, it said.
Caroline Flint MP, Labour’s shadow energy and climate change secretary, said: “The security of our energy supply has not been helped by the fall in investment under this government. With a quarter of our power stations closing this decade it is vital that we bring forward investment in secure and clean energy for the future.”
Andrew Whalley, a member of the British Wind partnership and CEO of REG, a British renewable energy generator, said: “Energy minister Matthew Hancock, rightly wants the cheapest low carbon energy, but nuclear power isn’t the cheapest answer. Onshore wind is already cheaper than new nuclear power: by 2020 it could become the cheapest of all new power generation technologies. The onshore wind pipeline snarled up in the planning process is vital to ensuring secure UK electricity at the lowest cost.”
CECA chief executive Alasdair Reisner said: “The future energy landscape in the UK will be challenging in terms of guaranteeing supply and managing demand.
“We have repeatedly said that only a long-term energy strategy which has full industry and cross-party support will ensure the continuation of a safe and secure energy supply to complement our economic and social growth.
“To achieve this effectively delivering Electricity Market Reform combined with better management of energy demand is vital.
“We call on Government to complete the implementation of Electricity Market Reform to secure investment in all of the low carbon sectors – renewables, carbon capture and storage (CCS) and new nuclear - and put energy efficiency at the heart of a long-term energy strategy.
“At the same time there must be Levy Control Framework clarity over the next decade to deliver low carbon deployment and ensure best value.”