By ED JOHNSON The British government Wednesday unveiled sweeping anti-terrorism legislation designed to crack down on Islamic extremism, raising concerns from Muslim leaders, opposition parties and legal experts about the potential for infringing on civil liberties. In the wake of the July attacks on London’s transit system, the government wants the power to detain terror suspects for three months without charge, outlaw attending terrorist training camps in Britain or abroad and make it an offense to glorify or encourage terrorism. “The terrorist threat facing the U.K. is real and significant and the government is determined to do all it can to protect our citizens from groups who would try to destroy our society, our way of life and our freedoms,” Home Secretary Charles Clarke said as the Terrorism Bill was published in Parliament. Opponents warned that the legislation, which must be approved by both chambers of Parliament before it can become law, could infringe on civil liberties. “We all need to be vigilant in ensuring that the government’s proposed measures do not jettison fundamental freedoms at the cost of providing little or no guarantee of extra security,” said Sir Iqbal Sacranie, secretary-general of the Muslim Council of Britain. The government has moved swiftly since the July 7 suicide bombings that killed 52 London commuters, and the failed July 21 attacks. It has widened its powers to deport foreign nationals who glorify terrorist violence, has proposed banning 15 international Islamic groups under existing anti-terrorism laws and wants to make it easier to strip British citizenship from dual nationals considered a threat. The Terrorism Bill also aims to outlaw preparing an act of terrorism, publishing or selling material that incites terrorism and giving or receiving training in terrorist techniques such as how to spread viruses, place bombs and even cause a stampede in a crowd. The most controversial proposal would extend the maximum detention period for terrorist suspects held without charge from 14 days to three months. Police and prosecutors argue that more time is needed in complex cases, in which suspects often have multiple aliases and store information in tightly encrypted computers, or where the cooperation of foreign agencies is needed. Prime Minister Tony Blair on Wednesday defended the measure and said police have made an “absolutely compelling case” for the extension. But Lord Carlile, appointed by the government to review the measures, said the three-month detention plan could be open to challenge under European human rights legislation.