By Mark Kinver
Science and environment reporter, BBC News
A looming "energy gap" could leave thousands of homes without electricity
The UK will experience prolonged power cuts in about five years unless urgent action is taken now, a report warns.
It said a third of generation capacity was due to be decommissioned by 2020, but was not being replaced fast enough.
The report, by nuclear supporting Fells Associates, said new reactors would not be ready in time, and questioned spending on renewable energy.
Energy Secretary John Hutton said the report overstated the risks and that the issue was a national priority.
The report was commissioned by Sheffield-based industrialist Andrew Cook, who voiced concern about a "fearful void" in energy policy.
The report - A Pragmatic Energy Policy for the UK - was compiled by Fells Associates, a network of energy and regulatory specialists.
Co-author Candida Whitmill said the so-called "energy gap" would also have severe economic consequences.
"The current credit crunch is a head cold compared to the double pneumonia this country will suffer if we don't implement an energy policy urgently," she told reporters.
"That is why security of supply now takes priority over everything, even climate change.
"If we are going to cope with climate change, it is going to cost money; if we want to protect the environment, it is going to cost money; and if we want to change to a low-carbon economy, it is going to cost money."
The report identified a number of factors that would combine to create the energy gap.
It said the main impact would be the loss of 23 gigawatts (GW) of electricity generation capacity between now and 2020.
The UK's ageing nuclear reactors, which currently provide about a fifth of the nation's electricity, are set to be decommissioned over the coming years.
Current projections show that by 2023, the UK will have only one nuclear reactor in operation.
And an EU Directive that requires the most polluting coal- and oil-fired power station to close would result in the likely loss of a further 12GW generation capacity.
Mind the gap
In its 2007 Energy White Paper, the government indicated that it was in favour of a new fleet of nuclear power stations.
But co-author Ian Fells said this strategy failed to address the short-term shortfall.
"Let's put it this way, the current UK energy policy is not fit for purpose," he told reporters at a briefing in central London.
"Something has to be done about it if we are not going to run into serious problems in the middle of the next decade."
Professor Fells warned: "It is all very well for the prime minister to decide that we need to build a lot of new nuclear power stations, but implementing that is really rather difficult."
He said that it was likely to be a further decade before any new reactors came online, which would not be soon enough to help bridge the looming energy gap.
The report also questioned whether government subsidies for renewable energy were the best way to spend public money.
Professor Fells said: "We have reached the stage where there is tremendous emphasis on renewable energy, and rightly so because renewables need to be an important part of the energy mix.
"But it is totally failing to meet the targets that were set.
"The UK is supposed to generate 10% of its electricity [from renewable sources] by 2010, yet it will be about 6%.
"It is more worrying that we have signed up to the European energy plan, which is 20% renewable energy by 2020 - that implies about 40% renewable electricity.
He added that government figures showed that subsidies for renewables last year amounted to £1bn.
"If we continue the way we are providing subsidies at the moment, that would gross at between £20bn to £30bn by 2020.
"This is a staggering subsidy that is being provided to keep renewable energy on the road."
Out of touch
Mr Hutton said: "Ian Fells overstates the risk of the energy gap, but he also understates what the government's already doing to secure our future supplies and increase our energy independence - such as a tenfold increase in renewables, a renaissance of nuclear energy in the UK, and backing clean coal technology."
He added: "That's not to underestimate the task we've got on our hands. Securing future energy supplies for the UK is a matter of national security and so we're not going to rule out any radical options.
"That's why we keep our energy infrastructure under constant review, and will continue to take the tough decisions needed to ensure that we have reliable energy supplies in the decades ahead."
Greenpeace UK's chief scientist, Doug Parr, said the global appetite for renewables meant the UK had to position itself as a leading player.
"All over the world, jobs are being created in the renewable energy sector," he said.
"But Britain has been left behind for too long by the negative, white flag approach to climate change that this report represents.
"Professor Fells has a long-standing love affair with the technologies of the 20th Century, but as time goes by his fetish for coal and nuclear power looks increasingly naive."
However, Mr Cook, the businessman who commissioned the report, said the assessment was in response to the government's "blindness to the reality of the situation".
"If nothing is done, within five years the UK could be beset by chronic power cuts," he warned.
"None of the measures which have been announced recently will be of the slightest use in the short and medium term."
The report's authors produced what they called a "route map" that illustrated ways to bridge the gap in the UK's generation capacity.
"The answer is that there is something that we can do about it," Professor Fells said. "But there are some unpalatable things that we need to do."
Measures within the route map included keeping "current nuclear power stations running long past their sell-by date, which is not a very sensible thing to have to do".
It also said that ministers had to consider keeping some of the coal-fired power stations earmarked for closure online.
"But there are other things that we could do quite quickly," observed Professor Fells.
"We could lay electricity transmission lines to Norway, Germany and Denmark. We could also lay another line to France.
"This would mean that we were properly connected to the European network, which would mean a greater amount of security and comfort.
"All of this could be done within three years, provided that someone is prepared to make decisions."