Half of London's businesses still do not have plans in place to deal with a terror attack or other emergency, according to the latest London Business Survey by the CBI and professional services firm KPMG.
In the past year businesses have had to cope with terror attacks on London's transport network, the Buncefield oil depot explosion, floods, power failures and the continuing threat of theft and fraud.
But only 47% of companies with a turnover of less than £5m (about 98% of the capital's businesses) have a contingency plan, the survey shows.
The survey found that the bigger the firm, the more likely they are to have contingency plans. More than half (56%) of firms with a turnover of £6m-£20m have a plan, rising to 79% for companies with a higher turnover.
Rick Cudworth, global service leader for business continuity services at KPMG, said that despite a perceived increase in threat levels, the figures were similar to those of 2005.
"This would seem to indicate that whilst there is plenty of guidance and help available in drawing up and testing plans, a proportion of London businesses still believe that it won't happen to them," he said.
He said the government needed to think about what help it could offer smaller businesses which perceived the cost to outweigh the risk.
"Recent wide-scale disasters show that whilst a company cannot predict what scenario it might face - it can rehearse for the unexpected," Cudworth said. "All firms need to work out how to keep a business working during a major operational disruption."