The government should reconsider its strategy on fighting extremism because it risks making the situation worse, the Joint Committee on Human Rights said.
The committee, in a report, urged ministers to "tread carefully" when trying to define extremism as it risked undermining relations with some communities.
"It is far from clear that there is an accepted definition of what constitutes extremism, let alone what legal powers there should be, if any, to combat it. It does not appear that the government so far has been successful in arriving at one," the report said.
Committee chair Harriet Harman told BBC, "The difficulty with that is -- again it's the definition -- for example, I don't respect religions that regard women as subservient, I don't tolerate the views or beliefs of people who think that homosexuality is a sin, but I'm clearly not an extremist on the path to violence."
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"To have draconian orders -- breach of which is a criminal offence -- without being able to describe the problem that you're trying to put these orders against, is a problem," he said.
It found that while there was agreement that tackling terrorism was a priority, but not on how to combat extremism.
"Extremism causes terrorism and broader social harms including hate crime, honour-based violence and discrimination. That is why we published a counter-extremism strategy which confronts all forms of extremist ideology head-on, supports mainstream voices, and builds stronger and more cohesive communities," a Home Office spokesperson said.
"This broad counter-extremism agenda is distinct and complementary to our prevent programme which safeguards those who may be vulnerable to being drawn into terrorism," the spokesperson said.