Britain's current and former watchdogs over terrorism legislation say that government plans to crack down on nonviolent extremism may go too far.

The governing Conservative Party has proposed new powers to criminalize extremist views that stop short of advocating violence. The plans have been criticized by religious and civil liberties groups.

Giving evidence Wednesday to Parliament's human rights committee, Independent Reviewer of Terrorism Legislation David Anderson said trying to define extremist speech would be all but impossible and might "do more harm than good."

His predecessor, Alex Carlile, said "I am very concerned about making unlawful that which we have always taken to be lawful." He said the law could potentially be used against Creationism and other non-mainstream views as well as against Islamic extremism.