Aon has released its 2006 Terrorism Threat Map in which it has said that despite the July bombings in London last year, the city's terrorism threat rating remains unchanged.

Paul Bassett, executive director of Aon's crisis management division, said: “London's 'elevated' rating was not affected by last July's terrorist attacks. It was not a case of ‘if' but ‘when' an attack would occur and that threat remains”.

Aon said that while the threat of terrorism worldwide is not diminishing, its nature is changing. Bassett added: “The war on global terrorism has severely impacted the capabilities of large groups such as Al Qaeda to mount another 9/11-style attack. This has led to an increase in smaller groups who are more likely to go for softer targets.”

Justin Priestley, director of Aon's crisis management division said the change in tactics needs a corresponding change in the attitude of businesses to their risk management strategies.

“Businesses need to keep abreast of developments in the terrorist world,” he said.

"Many businesses have woken up to the risk of material damage but they are still not paying enough attention to their liability to employees and visitors to their premises.

"They need to adopt a balanced approach tailored to their own particular needs. They must also ensure that they have robust plans and procedures in place and people competently trained to carry them through effectively,” he added."