Home Secretary David Blunkett has rejected suggestions that an attack in Britain by al-Qaeda is "inevitable".
David Blunkett: "I have not used that phrase."
The home secretary said there needed to be a balance between warning people and just making them "jumpy".
His comments follow Metropolitan Police Commissioner Sir John Stevens' warning after the train bombs in Madrid that an attack on London was "inevitable".
"I have not used that phrase," said Mr Blunkett, in an apparent rebuke to the police commissioner.
Mr Blunkett told the Sunday Telegraph: "Of course, I cannot give a 100% guarantee that we will not have an attack because of the nature of the threat and the dangers of suicide bombers.
"There has to be a balance between telling the truth and reassurance.
"Otherwise people are jumpy without it having a good effect."
The home secretary also discussed a White Paper which aims to combat organised crime and is being published on Monday.
Catching 'Mr Bigs'
The paper will outline new powers which will be handed to the elite FBI-style Serious and Organised Crime Agency.
It would propose a national witness protection scheme to encourage "supergrasses" to give evidence against crime bosses or "Mr Bigs".
A Home Office spokeswoman said: "If we are to encourage people to come forward and co-operate with law enforcement they need to be confident about arrangements for guaranteeing their safety.
"Most forces already have good individual systems in place.
"We are reviewing the case for bringing them together into a national scheme to improve quality, consistency and efficiency of the process."
Mr Blunkett also told the newspaper the White Paper would propose that phone tap evidence should be admissible in court.
"A year ago, if you had asked me, I would have been very sceptical.
"I am much more convinced that, in a limited range of cases, intercept evidence would make sense."
The paper will also force associates such as lawyers, bankers and accountants - who are normally bound by confidentiality rules - to disclose information about gangster clients, or face jail themselves.