Official government statistics published last week on the UK’s energy consumption in 2007 showed nuclear accounting for just 15% of the total electricity supply.
At just 52 TWh out of a supplied 378.5TWh, this is its lowest proportion since 1987 and down from 18% in 2006.
The statistics for 2008 are set to be even worse given that reactors at British Energy's Heysham 1, Torness, Hunterston B and Sizewell B plants have all suffered unplanned shutdowns for repair and maintenance in the past year.
Nuclear Industry Association chief executive Keith Parker said the declining influence of the UK's ageing nuclear plant meant urgent action was required if the country was to avoid the lights going off.
"It's not just nuclear coming offline, but all the old coal stations too," said Parker.
"We are facing a potential energy gap from sometime between 2016 and the early 2020s. Investment has to be made fairly urgently."
He added that urgent action, in the context of nuclear power station construction, meant planning applications for new facilities being submitted within the next two years.
Given this timescale, Parker played down French generator EDF's decision last week to withdraw from its planned £12bn purchase of British Energy.
"It is not a huge setback; it's still early days,” he said.
EDF's purchase was likely to hand it a monopoly over developing a new generation of nuclear power plants, but negotiations broke down.
The Government, a 35% shareholder in British Energy, remains keen on using its sale to kick-start the new nuclear process and business secretary John Hutton said: "I am disappointed that talks between British Energy and EDF have not yet been successful. It is a now matter for both Boards to see how to proceed.
"[However], nuclear new build does not depend on one single deal. British Energy still has potential sites, and sites are available from the Nuclear Decommissioning Authority.
"The level of interest in nuclear new build in the UK from
EDF and from other operators remains high."
The Government’s assumption that the open market will provide new nuclear in time to plug any potential energy gap was criticised by Parsons Brinckerhoff head of sustainable energy developments Ian Burdon.
"The Government can huff and puff, but at the end of the day the market is supposed to be delivering,” said Burdon.
"It will be the boardrooms of Paris and Madrid that decide whether nuclear is the most commercially advantageous way [of plugging the energy gap].
"Do we wait until 2020 for the market or do we plan other ways to keep the lights on in the meantime?"
Burdon was also sceptical of a report commissioned by environmental group Greenpeace and conservation group WWF, published last week, that claims Britain does not need to build major new power stations to fill the projected energy gap if it meets its renewable targets.
The report says that if the British government meets its European Union renewable energy targets, and its own plans to reduce demand through energy efficiency, then new coal or gas power stations power would not be needed before 2020.
"Are they suggesting that we wait until 2020?” asked Burdon.
"The rate we are progressing [with renewables] currently indicates that we won’t hit those targets. The UK needs a diversity of fuel supplies including coal, gas, nuclear and renewables."