LONDON — Prime Minister Brown set out plans for tough new antiterrorism laws yesterday, saying police need greater powers to hold and question terror suspects in increasingly complex and global plots.

Mr. Brown said there had been 15 attempted attacks in Britain since September 11, 2001. He said fighting Al Qaeda-inspired terrorism would last a generation.

Addressing lawmakers, Mr. Brown said one option was extending the time that police can question terror suspects. Currently, suspects need to be charged or released within 28 days.

Although Mr. Brown held off on specific proposals — new laws will be considered later this year — he told legislators that state of emergency laws could extend police custody to 58 days.

Another suggestion was to allow police to question suspects after they have been charged — not permitted under normal British laws — which Mr. Brown said could minimize the number of exceptions to the 28-day standard.

Mr. Brown is likely to face widespread opposition from lawmakers, civil liberties groups and some in Britain’s nearly 2 million Muslims who believe they are unfairly targeted by police profiling.

“These measures effectively mean the Muslim community will be the target, and in most instances, become the victims,” a spokesman for the Muslim Association of Britain, Ihtisham Hibatullah, said. Another option was to allow police to apply to judges for extensions beyond 28 days. Officers would need to seek permission every week from a judge and provide details of the case to Parliament, Mr. Brown said.