Home Secretary Sajid Javid is to reveal plans for MI5 to declassify and share information on UK citizens suspected of having terrorist sympathies.
The security services currently hold information on around 20,000 such people, labelled “subjects of concern”.
Intelligence around these people will be shared more across the government, local authorities and the police.
Mr Javid will make the announcement later in a speech relating to the overhaul of UK counter-terror strategy.
In his first speech on security since replacing Amber Rudd as home secretary, Mr Javid will suggest increased – and faster – sharing of information between security services, the private sector and other partners.
He is expected to say: “That includes faster alerts for suspicious purchases, improving security at crowded places across the UK, and reducing the vulnerability of our critical infrastructure.”
Meanwhile, ministers have said reports that dozens of terrorists are set to be released from prison after completing their sentences within the next few months are a “concern”.
Ministers want firms to raise the alarm as quickly as possible if they have evidence of unusual transactions – such as someone stockpiling large amounts of chemicals or acting suspiciously when hiring a vehicle.
The move reflects concern over a sharp reduction in the timeframe between the conception and execution of terror plots.
Mr Javid will say there has been a “step change” in the threat to the UK.
Other proposals in the speech will include increasing maximum sentences for some offences, enhancing the use of data to track terrorism suspects and outlining a new approach to deal with right-wing extremism.
“Ultimately, our approach is about ensuring that there are no safe spaces for terrorists. No safe spaces internationally, in the UK or online,” he will say.
Mr Javid, who on Sunday confirmed the security services were to get 2,000 extra officers, will also argue that the Islamic State group and right-wing extremists are “more similar than they might like to think”.
He is expected to say: “They both exploit grievances, distort the truth, and undermine the values that hold us together.”
It emerged over the weekend that security services expect the threat from Islamist terror to remain at its current heightened level of “severe” for at least another two years, while they assess that the risk from extreme right-wing terrorism as increasing.
Security minister Ben Wallace told the BBC that classified information would be divulged where “proportionate and necessary” – as he said had once happened in Northern Ireland.
The move was not aimed at “hardened plotters”, he told BBC Radio 4’s Today, but the “large pool” of people who might assist them in different ways, for instance by lending money.
The BBC’s security correspondent Frank Gardner said the number of people being talked about was “in the hundreds not the thousands”.
While officials were adamant that early intervention could protect those potentially vulnerable to radicalisation, he said there was a risk that entirely innocent people could find themselves “effectively blacklisted”.
Councils said they already played a role in reporting early signs of radicalisation but their staff could not be expected to do the jobs of intelligence experts or police officers.
“Information sharing could be a positive step,” said Simon Blackburn, from the Local Government Association.
“But local authorities are not MI5 and it’s essential that the police and security services lead on responding to and acting on any threats.”