Number 10 has refused to guarantee there will be no power cuts in the UK this winter amid warnings that millions of households could be hit by outages.
The government has drawn up plans for rationed electricity if supply issues deteriorate but Boris Johnson's deputy spokesman said power cuts are not expected and preparations have been made as a contingency.
Asked about the reports, Number 10 said: "I think you would expect government to look at a range of scenarios to ensure plans are robust, no matter how unlikely they are to pass. Neither the government or National Grid expect power cuts this winter.
"You will know that we are in a fortunate position, we are not dependent on Russian energy imports and have one of the most reliable and diverse energy systems."
The Times says limits could be imposed on industrial use of gas, including on gas-fired power stations, causing electricity shortages.
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As a result, six million homes could see their electricity rationed, primarily during morning and evening peaks, in curbs that may last more than a month.
Worse modelling is reported for a scenario in which Russia cuts off all supplies to the EU.
Asked about energy rationing, Mr Johnson's deputy spokesman added: "We don't expect energy rationing this winter. Again, we are in a different position to other countries in that we are not as dependent on Russian energy as some. You will know that we have access to our own North Sea gas reserves, and imports from other reliable partners.
"But again, I think you would expect us to plan for all scenarios."
A Department of Business, Energy and Industrial Strategy spokesperson told the PA news agency the UK “has no issues with either gas or electricity supply, and the government is fully prepared for any scenario, even those that are extreme and very unlikely to pass”.
“Thanks to a massive £90 billion investment in renewable energy in the last decade, we have one of the most reliable and diverse energy systems in the world,” the spokesperson added, “and unlike Europe, we are not dependent on Russian energy imports.”
But threats to security of supply have prompted Business Secretary Kwasi Kwarteng to ask Britain’s coal-fired power stations to delay their planned closures.
A government spokesperson told PA the request for the power stations in Drax, Ratcliffe and West Burton, which were due to shut in September, to stay open was made “in light” of the Russian invasion of Ukraine.
“It is only right that we explore a wide range of options to further bolster our energy security and domestic supply – bringing down costs in the long-term,” the spokesperson said.
“While there is no shortage of supply, we may need to make our remaining coal-fired power stations available to provide additional back-up electricity this coming winter if needed.
“It remains our firm commitment to end the use of coal power by October 2024.”