According to research from NCC, almost half of the UK's government bodies (47 per cent) would suffer a significant or catastrophic impact on their operations within 24 hours of a mains power failure.
"There's a degree of complacency," said John Redeyoff, director of NCC. "Because central government feels it is impervious to what may happen."
Government departments fared worst in the study, but telecoms and construction firms also came close.
But firms in the financial sector appeared to have higher standards, with 57 per cent claiming they were able to operate after a power cut.
"Financial services are really well equipped," said Redeyoff. "That's because they can count the cost impact to their systems. It's a bit more difficult with government systems because there's less of a correlation between service and money."