Britain's gas industry is on a knife edge this winter and could tip into crisis if there is a major breakdown in its aging North Sea fields and pipelines, analysts said.
Europe's biggest consumer is fast running out of gas from the fields that once made it self sufficient and kept UK prices among the lowest in Europe. Today, UK gas is the world's costliest fuel and winter supply will be the tightest in memory.
Government ministers are under pressure to explain how one of the world's richest nations has left its energy policy hostage to the weather and aging North Sea equipment.
"The crucial issue will be the unexpected happening in the North Sea," said Jonathan Stern of the Oxford Institute of Energy Studies. "North Sea kit is very old. Most was built between 1966 and 1986 and a lot is at the end of its life."
Industry has already cut back output because of high prices and newspapers are raising the spectre of a return to the three-day working week seen in the power crisis of the 1970s.
The government said on Thursday it was reviewing contingency plans. Energy Minister Malcolm Wicks told Parliament he held talks with companies in the summer to check they were maintaining their North Sea infrastructure adequately.
"I met representatives of the oil and gas industry... to make sure that they were doing the repairs and had the spares necessary to ensure that they were in the best possible position this winter," Mr Wicks said.
Ministers have conceded that if there is extraordinarily harsh weather, then gas supplies to some industrial consumers could be cut. They insist households will be protected. The greatest problem for the UK will be if there are breakdowns at large gas gathering terminals at St Fergus in Scotland and Bacton in Norfolk which process fuel coming onshore from North Sea fields, Mr Stern said.
"It has been such a long time since we have had any seriously cold weather for a prolonged period that we don't know how the electricity and gas networks will cope," he said.
Some weather forecasters, including Britain's Met Office, have predicted colder-than-usual temperatures this winter.
British consumers used to enjoy among the lowest gas prices in the European Union but costs have risen after oil prices surged and as the country becomes more reliant on imported gas through a pipeline from Belgium and in super-cooled tankers.
But Britain's neighbours are often unable to sell into the UK market - the most freely traded and competitive in the EU - because their gas markets are controlled by dominant former monopolies locked into long-term contracts.
Residential consumers, whose bills have climbed by more than 40 per cent over the last two years, are gearing themselves for more price hikes. The UK's import dependency has grown steadily since output from its North Sea fields started to fall five years ago.
More import projects are being built but most will only come on stream in 2006 and 2007.
The UK's gas output has fallen faster than expected, leaving a supply gap this year as most companies thought new supply would be needed in several years time.
Imports rose on Thursday after a ship carrying Algerian liquefied natural gas (LNG) docked at the new Isle of Grain terminal near London. Gas traders say three more LNG cargoes are likely to be on their way to Britain in December as companies cash in on the high prices.