Almost half of Britain's senior police officers are suffering from anxiety-related illness - with chiefs blaming the pressures of dealing with the increased terrorist threat after 11 September for the problem.

New figures published next month will reveal that 43 per cent of superintendents and chief superintendents are suffering from anxiety, and 17 per cent of these officers had such severe symptoms that they required medical help. Another 20 per cent reported they were suffering from depression, and others said they had been diagnosed with insomnia or hypertension.

The statistics, based on a poll carried out by the Police Superintendents Association of its 1,400 members, will be unveiled next month at their annual conference.

Kevin Morris, president of the Police Superintendents Association, said some of its members were working 12-hour days partly as a result of the increased workload created by the war on terror.

Mr Morris said: "The war on terror in some parts of the country has led to an increased workload for police and added pressure leading to stress. London has been particularly hard-pressed."

Mr Morris, a chief superintendent with Surrey police, also admitted that the police and security services were fighting a losing battle in attempting to wipe out terror groups such as al-Qa'ida.

"There is no way we are going to defeat terrorism," said Mr Morris.

"There is a controlling level where we can feel more secure, but terrorism has been part of people's lives for as long as we can remember."

Metropolitan police officers have been the most affected by the terror alert. Many have been seconded from routine patrols to increase the police presence in areas regarded as potential targets such as Westminster.

Next Sunday, police will also help co-ordinate a mock terror attack which will be staged at Bank underground station in the City of London.

Around 200 fire and ambulance personnel will take part in the exercise to improve their responses so they are prepared in the event of a real chemical attack on the Tube.

Public outrage over terrorist attacks, especially in the wake of the destruction of the Twin Towers, has been directed at members of the Muslim community. However, Mr Morris said that it was wrong to associate Islam with terrorism.

"What I find sad is that we bill these people as 'Muslim' terrorists," he said.

"There is nothing in the Koran that orders people to kill. It is the biggest prejudice that we keep referring to them [terrorists] as Muslim. These people are just extremists whatever their religion. You can just as easily get Christian fundamentalists."

He also branded the American public "pathetic" for refusing to fly abroad because of fears of terrorist attacks on board planes and criticised the strategies used by airlines to combat terrorists.

"I find it amazing that you can't get on a plane with a pair of tweezers but they will serve you a drink in a glass in club class," said Mr Morris.

"I was on a plane and there was an axe by the toilet."