A combination of poor business continuity and disaster recovery plans and inadequate back-up power supplies are the main weaknesses, according to IT assurance firm NCC Group, which commissioned the study from IRN Research.
IT managers and directors at 412 organisations were questioned about their contingency plans. Almost 70% of companies in the metals and machinery sector said they would face an IT shutdown within one hour of a black-out. Almost 50% of utilities, government, construction, and food organisations would also be down within the hour.
Some 33% of telecoms companies would be hit in the first hour, although chemicals firms (17%), retailers (13%) and financial services companies (9%) fared better.
About 64% of electrical and electronics companies said having their own back-up systems meant they could hold out indefinitely against a complete loss of external power. The only two sectors near this performance were financial services (57%) and retailing (61%).
Ian Fells, energy expert and former professor of energy conservation at Newcastle University, has warned that the UK could face similar power failures to those experienced in the US. "In December 2002 the UK was within three minutes of experiencing a serious blackout," he said.