The Home Secretary said he was optimistic that the group behind the blasts would be tracked down. But he told the BBC: "Our fear is, of course, of more attacks until we succeed in tracking down the gang that committed the atrocities on Thursday. That is why the number one priority has to be the catching of the perpetrators."
And John Reid, the Secretary of State for Defence, warned on Sky News that the bombers may try to attack again.
In a statement to the House of Commons today, Tony Blair will dismiss Conservative calls for an inquiry into whether there were intelligence failures before the explosions.
Downing Street sources said that he would give "short shrift" to the demand from Michael Howard, the opposition leader, and make plain he has full confidence in the security services. The Prime Minister will argue that such a move would be a distraction from the task of catching the bombers.
Mr Howard said: "Let's look again at our arrangements. Let's have an inquiry into what happened and whether anything more could have been done. I hope the Government will look again at some of the suggestions which have been made."
Mr Clarke will attempt to win backing for further British proposals to tackle terrorism in an emergency meeting of EU interior ministers he is to chair in Brussels on Wednesday.
Britain has floated most of the ideas before, but failed to win support for them. But Mr Clarke will argue that last week's attacks underline the need for EU leaders to examined them closely. His priority is requiring telephone companies to retain records of all private telephone calls, text messages and e-mails for six to 12 months.
"Telecommunications records, whether of telephones or of e-mails, which record what calls were made from what number to another number at what time are of important use for intelligence," he said. "I am not talking about the content of any call, but the fact that a call was made."
Other UK proposals include an up-to-date EU database of stolen weapons and explosives, extra work on the financial trail left by terrorists, sharing of all airline passenger information between EU states and security organisations and setting common security standards on national identity cards.
Mr Clarke confirmed that fresh anti-terrorism legislation, including a crackdown on acts described as "preparatory to terrorism", would be published in the autumn. He also said he would consider granting further "control orders" on terrorist suspects if he thought they were necessary.
Mr Howard urged the Government not to be panicked into rushing through any draconian legislation.
Charles Kennedy, the Liberal Democrat leader, appealed to the Government not to lose sight of civil liberties issues under such trying circumstances.
"The very thing that gives us the way of life we've got is the same concept that these people have got no respect for and would be quite happy to see trampled into the dust and that is individual liberty, justice, a proper democratic and judicial form of the rule of law generally," he said.
"Now that is fundamentally important and we've got to defend that because the minute we start conceding that, we're actually conceding some of the case that these people are trying to make in hating our way of life and the values that we take for granted."Reuse content