By Glenn Frankel London — Britain is drawing up a new blacklist to block alleged terrorist sympathizers from entering the country and deport those already here, officials announced Wednesday, detailing expanded efforts to head off violence such as the July 7 bombings. Officials also said they had reached an agreement to extradite Jordanian terrorism suspects to Jordan. Civil libertarians have expressed concern that the deportees could be subjected to torture and other abuses, despite Jordan’s pledges of good treatment. The crackdown is part of a government campaign to root out what it views as fundamental causes of the transit attacks, following the disclosure that the four men who appear to have carried out the suicide bombings were young British Muslims who turned into fanatics. At least 56 people, including the bombers, died in the attacks, and 700 were wounded. Britain has for years seen itself as a haven for political refugees, including some considered extremists by other European countries and the United States. But the bombings have caused the government to reconsider both its immigration policies and its tradition of freedom of speech. In Pakistan, authorities said they were searching for a man named Haroon Rashid, who they believe may have played a role in the attacks. They denied reports that they had arrested him. A man by that relatively common name was taken into custody, officials said, but then released when it was determined that he was not the person being sought. Senior Pakistani intelligence officials have said that, after early questioning of two dozen people suspected of being Islamic radicals, no clues about the terrorist contacts of the London bombers have been found. About 150 such suspects have been detained during a nationwide police crackdown in the past two days. Three of the apparent bombers were of Pakistani descent and visited Pakistan in the months before the attacks. The fourth man was a Jamaican-born convert to Islam. In London, the government hopes that the new measures under discussion will cut off or reduce the opportunities for radicals to influence alienated young Muslims in urban areas such as Leeds, the northern British city where three of the men lived. Charles Clarke, the Cabinet minister in charge of domestic security, told the House of Commons that the government plans to compile a database of unacceptable behavior, such as preaching extremism, running radical Web sites and writing articles intended to foment terrorism. He said he had asked his department and Britain’s intelligence services to “establish a full database of individuals around the world who have demonstrated relevant behaviors.” Those on the list could be barred from the country if their presence is judged as “not conducive to the public interest,” he said. “In the circumstances we now face, I have decided that it is right to broaden the use of these powers to deal with those who foment terrorism or seek to provoke others to terrorist acts.” Clarke also said he planned a new offense of indirect incitement to terrorism that would target “those who, while not directly inciting, glorify and condone terrorist acts knowing full well that the effect on their listeners will be to encourage them to turn to terrorism.” His statement won immediate backing from the opposition Conservative Party, which said it also wanted the government to regulate and vet Muslim clerics to weed out extremists. “There are good imams and bad imams, and it’s no help to the good imams if we don’t deal with the bad imams,” said David Davies, the party’s home affairs spokesman. Clarke also announced that the government had reached a memorandum of understanding with Jordan that would allow Britain to deport suspects there. Under international law, Britain cannot send people back to a country where they might face mistreatment or the death penalty, but officials said the memorandum, which was not released, included assurances that deportees would be treated correctly. Officials have said they are negotiating similar agreements with several other Arab governments. Amnesty International, the human rights organization, said it had compiled recent accounts from Jordan of secret detentions of political prisoners, beatings during interrogation with sticks and cables, sleep deprivation and threats of killing and rape against prisoners and their families. “Frankly, we think these assurances are not worth the paper they’re written on,” said Saria Rees-Roberts, an Amnesty spokeswoman. “It’s just unacceptable for the U.K. to try to circumvent the global ban on torture. We believe the U.K. must bring the people responsible for the bombings to justice, but going soft on torture is not the answer.” One of those likely to be targeted for deportation is Abu Qatada, a Jordanian-born cleric who has been convicted of terrorism in absentia in his native Jordan. The authorities branded him as one of the spiritual fathers of the Sept. 11, 2001, attacks in the United States, after police found tapes of his fiery anti-Western sermons at the Hamburg apartment used by some of the Sept. 11 hijackers. Qatada was arrested three years ago on suspicion of terrorism and is under house arrest in London, but authorities say they have been unable to bring him to trial because much of the evidence against him is based on intelligence data that they do not want to reveal in court.