The UK's counter-terrorism strategy must be broadened to all communities so it doesn't appear to target Muslims, says Labour leader Jeremy Corbyn.
The Prevent scheme was "often counter-productive" and appeared to cast suspicion on all Muslims, he told ITV.
Far-right extremism and racism must also be dealt with, he said.
Conservative peer Baroness Warsi said Prevent was "broken". Home Secretary Amber Rudd said she recognised the need "to sell it to communities".
Prevent is a multi-agency programme which aims to stop people being drawn into terrorist-related activity in sectors "where there are risks of radicalisation" like prisons, education, health and online.
Khalid Masood killed three people and injured 50 when he drove a car into pedestrians on Westminster Bridge on Wednesday.
The 52-year-old then fatally stabbed a police officer before being shot dead by police - all within 82 seconds.
Deputy Assistant Commissioner Neil Basu said detectives believed Masood had acted alone and added that there was a possibility that his motive may never be known.
Following Wednesday's attack, Mr Corbyn suggested the government's counter-radicalisation programme needed to be changed.
He told ITV's Peston on Sunday: "I talk to people in the Muslim community, I talk to people in mosques, I talk to people in churches, I talk to people that go to synagogues, all kinds of different faiths and different groups.
"I think what Prevent has often done is seen to target the Muslim community, not anybody else, looks to say there is a kind of suspicion over the whole community and it's actually often counter-productive."
He said: "Deal with the issue of far-right extremism within our society, deal with the issue of racism in our society, deal with the issues of discrimination within our society, deal with the issues of the perceptions of stop and search within our society, above all be inclusive of people and what Prevent does, it says 'hang on, let's look at only the Muslim community'."
Pressed on what he felt needed to change, he said: "I'm saying broaden it into an agenda of inclusion ... Focus it on all communities."
The Home Office has said the Prevent strategy plays a key role in the fight against terrorism, but it has faced criticism, including from some British Muslims, who say it alienates them.
Conservative peer Baroness Warsi, who was minister for faith and communities between 2012 and 2014, told BBC One's Andrew Marr Show the scheme should be "paused" for an independent review.
She told the programme: "There is a lobby out there which absolutely trashes Prevent and says we don't need it, there's another lobby out there which says it is absolutely perfect ... I think the reality is somewhere in between.
"I think Prevent in its current form has huge problems, I think it's broken, I think the brand is toxic, I think there are question marks about the training, the trainers, the quality of training within schools, about how it is being implemented."
She called for it to be reviewed, adding "A prevent-like strategy" was needed which was "deeply trusted by the communities that it is trying to engage."
Home Secretary Amber Rudd rejected the call for a "pause", telling the BBC: "I think that now is exactly the wrong time to have a pause. What we have seen this week reinforces the need to make sure we have active communities trying to stop people becoming radicalised.
But she added: "I do recognise what Baroness Warsi said about needing to make more of an effort to sell it to communities: "We need to do better there to show that this is a safeguarding initiative, it's about protecting young people."