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”.

Mr Javid will make the announcement later in a speech relating to the overhaul of UK counter-terror strategy.

Mr Javid is also expected to say he wants to eradicate “safe spaces” that are exploited by violent extremists.

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.”

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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.

Mr Javid 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.

On Sunday, Mr Javid confirmed the security services were to get 2,000 extra officers as part of a strategy to boost the UK’s counter-terrorism efforts.

Speaking to the BBC’s Andrew Marr Show, Mr Javid vowed to make sure the UK had all the resources needed “to fight the terror threat”.

He said the threat was “top of my mind” and “something I think of every day”.