Alan West told BBC radio that the scale of the security operation was "quite dramatic" as he backed extending the 28-day limit on the time suspects can be held without charge.

He issued the warning following three botched car bombings in London and Glasgow at the end of last month -- attempts that came just days after Gordon Brown succeeded Tony Blair as prime minister.

"I have come back to this after about 16 months away from it and I have to say I was quite concerned when I saw what the level of threat is," said Lord West, the former chief of defence intelligence and now the security and counter-terrorism minister.

"If one looks at what our security service and police are looking at on a day-to-day basis, they are now monitoring over 200 groupings or networks which to varying degrees are threatening our security," he told the BBC.

"There are 30 that are actually being looked at very closely indeed because they have got to the stage where they are gathering materials and doing things which could lead in fairly short term to doing something if they wanted to.