London's ability to respond to a "catastrophic" terror attack will be tested within the next few weeks, David Blunkett has said.
The announcement follows an exercise in Harrogate on Monday, where emergency service leaders were shown how a decontamination unit would deal with the aftermath of a dirty bomb attack.
The government also announced the creation of a new website - www.homeoffice.gov.uk/terrorism - which it said would give advice to concerned members of the public.
Earlier, a senior government adviser told the BBC of his fears that Whitehall "lethargy" towards the possibility of a smallpox bio terror attack left the UK at risk.
And increased fears of a terrorist attack at Devonport Naval Base in Plymouth have led to Ministry of Defence police there being issued machine guns.
The London drill, announced by Mr Blunkett in a written statement to MPs, will cover mass-evacuation and also test the ability to decontaminate affected areas.
The precise nature of the simulated attack is unclear, but it could be based on the possibility of contamination caused by a dirty bomb.
Mr Blunkett told MPs that the exercise followed the 11 September attacks in New York although he urged the public to remain calm.
Further exercises to test the UK's preparedness for attacks on flood defences and the national gas supply are planned.
"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 Mr Blunkett.
"Future planned exercises will cover a catastrophic incident in central London - this exercise will take place shortly - disruption to the national gas supply and flood defences."
Liberal Democrat health spokesman Evan Harris said that the public needed hard copies of what to do in the event of an emergency as government websites might crash through demand.
In Harrogate emergency services leaders from across the UK were shown the aftermath of a staged terrorist attack.
Fake smoke was set off and sirens, pre-recorded screams and wailing used to imitate casualties from an attack.
The officials were shown a decontamination unit and how it could be used to deal with a chemical, biological or nuclear attack.
They saw how it would have to handle up to 100 victims an hour, who would be moved on to treatment sections before being taken to hospitals in waiting ambulances.
Earlier on Monday a leading government adviser, who wanted to remain anonymous, told BBC Radio 4's Today programme there was lethargy in Whitehall about the threat of a smallpox attack.
He suggested that official secrecy might be being used to hide inaction and that the UK, unlike France and the USA, did not have enough vaccinations for its entire population.
It's important that there shouldn't be a panic about it but equally it's extremely important that the country should be properly prepared
Tory, home affairs
In the US President George W Bush very publicly had the inoculation.
Responding to the criticism, a spokesman for Tony Blair insisted that proper plans were in place to cope with a smallpox attack.
There were enough stocks to contain any outbreak and 12 regional smallpox response groups were being established throughout the UK, the spokesman said.
"It is prudent that the government, faced with a very real threat from international terrorism puts in place appropriate contingency plans.
"We are not going to put into the public domain details of our stocks because that would possibly helpful to terrorist organisations."
Conservative home affairs spokesman Oliver Letwin told Today there was no point in starting mass vaccinations when there was no specific threat, but the treatment should be available to those wanting it.
The government adviser also said that Britain lags the US in terms of conducting drills to prepare for an attack.
The US has a computer simulation that analyses the effects of an attack and has been practising for emergency situations.
The UK's computer simulation is throwing all sorts of situations the nation is not prepared for, the adviser suggested.
"The British government is not doing enough. There's lethargy in government departments and classified material is a double-edged sword," he said.