More than half of all UK companies with a city centre headquarters are concerned about the safety of their building following the WTC attacks, according to a survey by international property adviser GVA Grimley.
Of these, 71% said their security concerns may make them reconsider their location. While in London specifically, 62% said security concerns would make them strongly consider moving offices.
The survey also showed a reluctance to work in tall buildings after the attacks - nearly half of those surveyed said they would not willingly work in a building of more than 20 storeys.
However, many companies had little or no plans to improve - with only 11% actively improving their security.
A spokesman for GVA Grimley commented: "Although the events of 11 September have made companies think more carefully about the safety and security of their HQ buildings, many appear to be adopting a complacent approach to shoring up their security arrangements.
"There is a whole raft of potential risks to property and business - including fire, flood and power failure - which could have a serious and long-lasting effect without adequate precautions and back-up," he added.
