SCOTLAND is on the brink of an energy crisis, a leading expert has warned, after it emerged the country has begun to rely on electricity produced in England to keep the lights on.

In a departure from historical trends, Scotland imported power from down south on 162 days over the past three years.

On 10 occasions, Scotland imported English power constantly throughout the day to meet its needs.

The previously unreported National Grid figures show Scotland continues to export far more power to England than it imports from south of the Border.

Overall, Scotland needed English-produced electricity for seven per cent of the time between April 2011 and January this year.

However experts warned Scotland's historic self-sufficiency in energy faced further erosion as nuclear and coal-fired power stations are due to close or cut capacity in the coming years.

Professor Paul Younger, Scotland's leading expert on energy engineering, said the growing need for English electricity revealed "increasingly tight margins" in Scotland's baseload (constantly available) and dispatchable (available on demand) electricity sources.

He said: "It's the thin end of the wedge. We really are facing a crisis in baseload and dispatchable generation.

"I'm proud Scotland is going forward with renewables. I'm all for renewables but the drawback is that most are unpredictable."

The Glasgow University academic added: "It's all right having your heart in the right place but if your head is not there you are going to come unstuck."

Scotland's two nuclear power stations, Hunterston B and Torness, which produce more than a third of Scotland's power, are due to close in 2023.

Coal-fired Longannet is expected to reduce capacity as a result of carbon emissions targets, while gas-fired Peterhead has already seen major reductions in output.

It is understood that Scotland's reliance on English electricity increased last year after the closure of coal-fired Cockenzie power station.

The problem was recognised in a report by the Scottish Government's expert commission on energy this week, which warned: "Under current forecast scenario ... Scotland is likely, at times of low renewables availability, to import electricity from rUK in order to continue meeting demand and for necessary network ancillary services."

The commission concluded that maintaining Britain's single energy market was "the best outcome" for producers and consumers if Scotland became independent. However the UK Department for Energy and Climate Change said the single energy market "would not continue in its current form". It warned Scotland would lose ­subsidies currently paid by UK consumers to support green power generated in Scotland. Tom Greatrex, Labour's shadow energy minister, said: "The reality is with an expansion of renewables funded by consumers across the UK and the SNP's ­opposition to nuclear power, we have an increasingly imbalanced energy mix in Scotland.

"For England and Wales there is a range of choices to buy power from, but Scotland is increasingly reliant on baseload power generated in England when the wind is not blowing."

A Scottish Government ­spokeswoman said: "Scotland's abundant energy resources continue to play a vital role in delivering security of electricity supply across these islands.

"Last year, Scotland generated a record amount of electricity from green energy sources, energy that is vitally needed when the UK is facing the highest black-out risk for a generation."