The number of potential extremists flagged up by members of the public to the Government's anti-terror scheme has doubled after Britain was hit by a flurry of attacks.
Police received around 200 referrals to Prevent from within communities from April to the end of July - compared to approximately 100 in the previous four months.
The rise in tip-offs coincides with the spate of terrorist incidents that began with the Westminster atrocity on March 22, followed by attacks in Manchester, London Bridge and Finsbury Park.
Disclosing the latest figures, Simon Cole, the national policing lead for Prevent, also said there was an "ongoing debate" over whether participation in the scheme, which is currently voluntary, could be made compulsory in some cases.
He welcomed the rise in referrals from communities but called for more members of the public to make contact.
Mr Cole said: "We have recently seen the devastating effects of what can happen when radicalisation is allowed to fester unchecked.
"On the one hand it is encouraging that more people are contacting police with their referrals.
"But if we are to successfully stop vulnerable people from being drawn into violent extremism, then family members, friends and community leaders must trust us sooner with their concerns.
"Not only will that possibly stop another lethal terrorist attack from taking place, but it will also potentially prevent vulnerable people from being drawn into criminal activity from which there is no coming back."
Police Prevent teams are receiving calls from other agencies and members of the public at a rate of around 20 a day.
There were about 6,300 referrals to Prevent in 2016/17 but fewer than one in 10 originated from within the community.
Mr Cole said: "I would like to see that increase. If you don't feel able to let us know, let another agency know, let someone you trust in your community know. Please don't sit on it."
The share of Prevent referrals relating to concerns about extreme right-wing ideology has doubled to around 15%, while 55% to 60% are linked to Islamist extremism.
Engagement with the scheme is voluntary and it is not a criminal sanction. Not all referrals are ultimately deemed to require intervention in the anti-extremism sphere.
On the issue of whether Prevent should be compulsory, he said: "I think that's a really interesting question.
"What do you do with returners (from Syria)? Should they have to automatically go on a programme?
"There's a bit of me at the moment thinks the fact this is a voluntary scheme is a good thing.
"But I can accept there might be some categories of people for whom there is some compulsion and that needs linking into risk.
"It's a debate that is ongoing at the moment and I don't think there's an easy answer.
"If someone is compelled to do something they might do it with a different approach that isn't as effective as if they were doing it voluntarily."
Prevent has been credited with playing a role in disrupting more than 150 attempted journeys to the conflicts in Iraq and Syria.
But the programme has repeatedly come under fire, with critics labelling it heavy-handed and "toxic" amid claims it unfairly focuses on the Muslim community.
Mr Cole, the chief constable of Leicestershire Police, acknowledged there are people with genuine and legitimate concerns but he issued a staunch defence of the scheme.
He said: "This notion of Prevent as a 'toxic' brand is simply incorrect, and is borne from misunderstanding.
"What I would like to hear more of is constructive dialogue about how we can all work together to stop innocent people being killed.
"On occasions it feels like people are sniping for the sake of it and that what they're talking about doesn't reflect the reality of local delivery of the voluntary safeguarding that I see going on all across the country."
The senior officer addressed controversy over referrals of young children.
"What do we do with a child who's been sat down and shown beheading videos? I'm aware of cases where children who are five, six, seven years old, have been sat down and shown videos of people being beheaded," Mr Cole said.