Alex Carlile told the Home Affairs Select Committee that credentials of as many as 20 imams who had arrived in the country had not been scrutinized, and that there was a "real and present danger" of more suicide attacks, such as those last July in London.
"My worry is that they are in places such as colleges and custodial institutions where there are larger numbers than elsewhere of impressionable young men," Carlile told the committee.
Since July, some prisons dismissed their imams after they were discovered distributing extremist literature to young inmates, The Times of London said.
Last week, radical imam Abu Hamza was jailed for inciting hatred, and also faces a U.S. extradition request on terror-related charges. Several of the bombers from the July 7 attack on the London transit system were known to have attended his mosque.