Home Secretary Charles Clarke says he remains "worried" about the possibility of further attacks following the July bombings in London.
Mr Clarke praised the Met Police
Speaking after a meeting with the UK's top police officer Sir Ian Blair, Mr Clarke stressed there was no specific intelligence on further attacks.
But he said it would be "foolish" to think the threat had been "eliminated".
Sir Ian said the fact that there had been two attacks made further bombings "more rather than less" likely.
Mr Clarke said he was "absolutely impressed" with the work of the Metropolitan Police since the bombings, saying real progress had been made.
But he said the risk of further terror attacks remained and was being dealt with.
"We remain worried. The commissioner has been very clear throughout that it would be ridiculous for us to assume that a further act would not take place.
"Obviously, one of the main purposes of the investigation - which is rolling ahead very strongly at the moment - is to identify any linkages which would help us act more effectively to be able to reduce that likelihood - and that work is happening," Mr Clarke said.
"The police, together with the other security services, are doing an excellent job.
"But it would be absolutely foolish for me, or for anybody else to say that we've eliminated the risk. We haven't.
"The risk needs to be contested and that's what we're doing."
Mr Clarke made clear there was no intelligence available of any specific threat of a new terrorist attack.
"There's no particular intelligence that we are addressing from that point of view.
"But we are working on the basis that the people who organised these attacks could proceed with other attacks as well.
"And that seems to me the only rational basis on which we should proceed."
Metropolitan Police chief Sir Ian said: "The fact that there's been two attacks makes it more, rather than less likely that there'll be further attacks.
"I mean, that's just the logic of all this, but we of course are working incredibly hard with the intelligence services to prevent it".