Ambulance bosses in Sussex have ordered 100 chemical protection suits as part of preparations for a terrorist attack.

Details emerged today as the Government announced plans to simulate a "catastrophic incident" over the next few weeks.

The chemical suits ordered by Sussex Ambulance Trust will allow health workers to safely treat members of the public in the event of an attack using smallpox or a "dirty bomb".

Negotiations are taking place with local NHS trusts on the best way of establishing decontamination facilities.

Home Secretary David Blunkett unveiled plans to test whether Britain is prepared for a terrorist attack.

He will assess central London emergency services on their reaction to mass evacuations and decontaminations.

The exact nature of the exercise has not been revealed but it is likely to be based on the scenario of a dirty bomb strike on the capital or a biological attack.

Other exercises are planned to test Britain's ability to withstand attacks on flood defences and the national gas supply, Mr Blunkett said.

"Under this new programme of co-ordinated exercises it will be possible to test whether all key stakeholders are appropriately engaged and working together," said the Home Secretary.

"Future planned exercises will cover a catastrophic incident in central London."

In his statement, Mr Blunkett also revealed more detail of the new military Civil Contingency Reaction Forces, or CCRFs.

By the end of the year 14 forces will be in place with up to 500 volunteers drawn from existing reservists.

Mr Blunkett confirmed that in the event of a terrorist strike, deployment of the military, including reserves, would be at the request of the chief constable in the force area where the incident occurred.

Of the CCRFs, he said: "Each will be based on a Territorial Army infantry battalion.

"Army division and brigade headquarters will provide regional planning, liaison and command and control capability for home defence operations.

"Brigades will work closely with the emergency services and local authorities to develop plans for the use of CCRFs."