Prisoners who pose a terror threat may have to remain behind bars far beyond their normal release date.
Hundreds of inmates jailed for non-terror offences who are feared to hold extremist sympathies could be refused the right to automatic release.
The radical changes to sentencing rules will be the centrepiece of legislation set to be published early next year.
Sources said the measures would apply to criminals numbering ‘in the low hundreds’.
Hundreds of inmates jailed for non-terror offences who are feared to hold extremist sympathies could be refused the right to automatic release (pictured, the Westminster terror attack)
The proposals would fundamentally change the way the criminal justice system handles the release of extremists and terror suspects and are likely to put ministers on a collision course with human rights lawyers.
Currently, the security services are powerless to keep extremists behind bars if they were found guilty of non-terror offences.
Some of the offenders who are expected to be subject to the new rules may have been acquitted of terror charges but convicted of other crimes, such as firearms or fraud.
In such cases, they are entitled to automatic release from jail after serving just half of their sentence.
Alan Mendoza, executive director of the Henry Jackson Society, an anti-extremism think-tank, has described existing sentencing rules as a ‘loophole’, adding: ‘The Government need to close it, and fast.’
Under the proposals, such offenders will have automatic release cancelled and their cases will be referred to the Parole Board.
They will be freed only when experts on the board agree they no longer pose a danger to the public – meaning they could remain behind bars until the very end of the jail term handed down by a judge.
The bid to extend sentences is likely to face challenges. Previous moves have led to appeals under human rights laws.
The Government’s emergency measures, passed earlier this year in the wake of the London Bridge and Streatham terror attacks, have been controversial because they extended automatic release to the two thirds point of a jail term for anyone convicted of terror offences.
A man who admitted terror offences challenged the measures in the courts, claiming they unfairly targeted Muslims.
Mohammed Zahir Khan, a former shopkeeper from Sunderland, pleaded guilty in 2018 to five counts of encouraging terrorism, one count of dissemination of an Islamic State terrorist publication and two counts of stirring up religious hatred.
Khan appealed against the measures on the grounds they were discriminatory – but his claim was rejected by judges last month.
The new measures are to be included in a white paper due to be published within weeks.
It will be followed by a sentencing Bill to be brought before Parliament by Justice Secretary Robert Buckland early next year, it is understood.
A Ministry of Justice spokesman last night declined to comment but added: ‘A white paper will be published shortly.’
How new rules could have stopped Westminster attack
By David Barrett
The Westminster Bridge terrorist could have been kept in prison for longer had the latest detention proposals been in operation at the time of his original sentences.
Before his murderous rampage in 2017 which killed five, including PC Keith Palmer, Khalid Masood had been in jail for a series of non-terror offences.
Before his murderous rampage in 2017 which killed five, including PC Keith Palmer, Khalid Masood (pictured) had been in jail for a series of non-terror offences
Masood, 52, drove a 4×4 vehicle at pedestrians at speeds of up to 76mph before fatally stabbing the police officer outside the Houses of Parliament and then being shot dead.
Although it is unlikely that such new laws would have led to Masood still being imprisoned at the time of the attack, they could have led to closer scrutiny of his beliefs during and after his various spells in prison.
The proposed tough measures could also – in theory – have been deployed in the case of gunrunner Nathan Cuffy.
The 30-year-old Muslim convert, from west London, who is also known as Ismael, was cleared of preparing terrorist acts and conspiracy to murder – but convicted under firearms laws, and handed an 11-year sentence in 2016.
The security services and the Government were powerless to prevent Cuffy’s release earlier this year.
If these new powers had been in force Cuffy could potentially have been kept inside until 2027.
Another terror attack, which claimed a number of lives, could potentially have been prevented by the measures had they been in force.
The alleged assailant in that case cannot be named for legal reasons.