Anti-nuclear demonstrators yesterday disrupted an announcement by the Prime Minister of a review into the UK's energy needs.

As Tony Blair was preparing to unveil details that could lead to a new generation of nuclear power stations being built, two Greenpeace activists scaled the roof structure of a conference hall, delaying his address by an hour.

They dropped hundreds of coloured stickers on delegates at the Confederation of British Industry (CBI) conference in London, forcing Mr Blair to make his speech in a smaller hall nearby.

The protestors, Huw Williams and Nyls Verhauelt, were arrested on suspicion of aggravated trespass.

They had gained delegate passes last week by giving the name of a bogus company and smuggled metal harnesses through the security cordon at the Business Design Centre, in Islington.

When he eventually delivered his speech, Mr Blair confirmed details of the energy review, saying the issue was "back on the agenda with a vengeance".

He said: "Round the world you can sense feverish rethinking.

"Energy prices have risen. Energy supply is under threat. Climate change is producing a sense of urgency."

Mr Blair said the review would be led by Energy Minister Malcolm Wicks and would aim to publish a statement on future policy early next summer.

"It will include specifically the issue of whether we facilitate the development of a new generation of nuclear power stations," the Prime Minister said.

He acknowledged that nuclear power was a difficult and challenging issue, adding: "What we need is a serious debate, not one conducted by protest or demonstration to stop people expressing their views."

The Government will look at nuclear power along with renewables, coal, gas and new technologies as part of the review, Mr Wicks said.

The move, which comes nearly three years after the last landmark investigation into the country's power supplies, will also include transport and the role of energy efficiency.

The aim of the review was to ensure "clean, reliable, affordable energy supplies for the long term", said Mr Wicks.

Industry and trade unions welcomed the announcement, although environmental groups warned they would step up protests against nuclear energy.

Stephen Tindale, director of Greenpeace UK, said: "Nuclear power is not the answer to climate change - it's costly, dangerous and a terrorist target.

"Just three years ago, Blair conducted the biggest energy review in 60 years, which concluded renewable energy and energy efficiency, not nuclear, is the way forward.

"Today's new review is simply a smokescreen for pushing his new-found enthusiasm for nuclear power."

Sir Digby Jones, CBI director-general, said: "This country urgently needs a revamped and coherent energy policy which includes a clear decision on nuclear power.

"Today, the Prime Minister has promised the Government will make that decision. That pledge is as vital as it is welcome."

David Willetts, Shadow Trade and Industry Secretary, said: "This energy review has become essential.

"We know from leaked documents that DTI (Department of Trade and Industry) civil servants told their ministers immediately after the election that they needed to have an energy review, but it has taken a gas supply crisis and rocketing fuel bills to force the Government finally to act.

"People want to know that when they flick the switch the light will come on; that their fuel bills are affordable; and that we meeting our targets to cut CO2 (carbon dioxide) emissions.

"A modern flexible market can achieve these objectives. But instead, Labour's fiddling with the energy market means that we are in danger of failing on all three fronts."

Liberal Democrat leader Charles Kennedy warned of the possibility of a "nuclear tax" if the Government commissions a new generation of atomic power stations.

He said: "The Department of Trade and Industry has made no assessment of the costs of the construction of new nuclear power stations."