Emergency legislation to delay the release of terrorist prisoners could create a dangerous “cliff edge” where they are freed without any restrictions, the government has been warned.

Under plans announced in the wake of the Streatham attack, which was launched by a terror convict days after he was released from jail, automatic release will be cancelled for inmates who have already been sentenced.

The Parole Board does not currently have any say in the release of terror offenders on determinate sentences like Sudesh Amman, who are freed halfway through their term regardless of risk.

But under the new law the board would assess all inmates convicted of terrorism and keep them inside for longer if they are still thought to be a threat.

The Independent Reviewer of Terrorism Legislation warned that offenders would still have to be released at the end of determinate sentences, which are currently served half in prison and half under licence.

Streatham attack: Man shot dead by police after stabbings Show all 22 1 /22 Streatham attack: Man shot dead by police after stabbings Streatham attack: Man shot dead by police after stabbings Armed police officers on Streatham High Road. The Metropolitan Police warned people to stay away from the Streatham area boguta37/PA Streatham attack: Man shot dead by police after stabbings The man was shot dead by police after two stabbed in 'Islamist-related' terror attack in London boguta37/PA Streatham attack: Man shot dead by police after stabbings Sudesh Amman, the attacker, has been named as a convicted terror offender who was released from prison days ago Metropolitan Police/PA Streatham attack: Man shot dead by police after stabbings Items left on the pavement at the scene in Streatham High Road Isis supporter Amman was just 18 when he was jailed in December 2018 after police found a stash of bomb-making manuals and other propaganda. Now 20, he had declared his own wish to carry out a terror attack and stockpiled a combat knife, air gun and black flag at his family home in London PA Streatham attack: Man shot dead by police after stabbings He was being monitored by undercover police and being followed as part of a “proactive counterterrorism operation” when he started the rampage in Streatham AP Streatham attack: Man shot dead by police after stabbings Amman was able to stab two people before being shot dead by armed officers outside a busy row of shops Gabriel Video/PA Streatham attack: Man shot dead by police after stabbings A woman reacts as police officers interview people near to the scene Getty Streatham attack: Man shot dead by police after stabbings An armed police officer on Streatham High Road Deputy Assistant Commissioner Lucy D’Orsi said Amman was wearing a fake suicide ves Gully/PA Streatham attack: Man shot dead by police after stabbings Police forensic officers work outside of a Boots store AFP via Getty Streatham attack: Man shot dead by police after stabbings Police officers at the scene Getty Streatham attack: Man shot dead by police after stabbings A police forensic officer works at the scene in Streatham High Road PA Streatham attack: Man shot dead by police after stabbings Items left on the pavement at the scene in Streatham High Road PA Streatham attack: Man shot dead by police after stabbings A police officer on the scene Dave Chawner/SWNS Streatham attack: Man shot dead by police after stabbings Police forensic officers are seen near the site Reuters Streatham attack: Man shot dead by police after stabbings Police officers on the scene outside an Iceland supermarket Andy Bullemor/SWNS Streatham attack: Man shot dead by police after stabbings Police are seen near a site where a man was shot Reuters Streatham attack: Man shot dead by police after stabbings A policeman secures the site of the incident EPA Streatham attack: Man shot dead by police after stabbings A view of the scene Megan Tobeck Streatham attack: Man shot dead by police after stabbings Armed police at the scene in Streatham High Road PA Streatham attack: Man shot dead by police after stabbings A view of the scene Michael Owens Streatham attack: Man shot dead by police after stabbings Police forensic officers at the scene PA Streatham attack: Man shot dead by police after stabbings A Police officer is seen near a site where a man was shot Reuters

“The difficulty which any new legislation will have to address for this cohort of terrorist offenders is, what happens if the Parole Board refuses to release the offender before their sentence expires?” Jonathan Hall QC told The Independent.

“If their sentence has expired, they cannot be released subject to conditions, and cannot be recalled for bad behaviour. There is a real risk of unintended consequences.”

Mr Hall urged the government to avoid creating a “cliff edge” where terror offenders are freed from prison without licence conditions, which can include deradicalisation programmes and restrictions on internet usage, movement and association.

The warnings come as one of the victims of the attack was named in reports on Tuesday as teacher Monika Luftner.

In a statement, St Bede’s Catholic Infant & Nursery School in Lambeth said a member of staff was making a “good recovery after experiencing a shocking attack”.

On Monday, Robert Buckland told MPs emergency legislation would see the Parole Board risk assess terror convicts for potential release after serving two-thirds of their sentence, rather than the current half.

“The underlying principle has to be that offenders will no longer be released early automatically and that any release before the end of their sentence will be dependent on risk assessment by the Parole Board,” the justice secretary added.

“We will ensure that the functions of the Parole Board are strengthened to deal even more effectively with the specific risk that terrorists pose to public safety.”

Mr Buckland said emergency legislation would apply retrospectively to terrorist prisoners given standard determinate sentences like Amman’s.

Downing Street said there would also be a full review of the maximum prison sentences for terror offences, including looking at whether offenders of all levels of seriousness should be held in jail indefinitely until the Parole Board assesses they are no longer a threat to the public.​

The plans have raised concerns over radicalisation inside British prisons, where recent cases have shown that terrorists are able to network and spread extremism.

Amman was shot dead by police on Streatham High Road (PA)

Amman’s mother claimed he had been further radicalised inside HMP Belmarsh, where a former inmate told The Times he openly stated his wish to carry out a terror attack and conducted a mock Isis execution.

There are already up to 800 flagged extremists in British jails – almost four times the number of terrorist prisoners – and there have been repeated official warnings about Islamist radicalisation including from the Parole Board and a government review.

The Prison Reform Trust urged the government to “proceed with caution”.

Director Peter Dawson said: “Terrorism has always posed a very particular set of challenges for criminal justice systems.

“There are examples from history both in this country and overseas where poorly thought through or disproportionate reactions are likely to have made things worse rather than better in the long run. Unfair treatment or disproportionate punishment are both effective recruiting sergeants.”

Downing Street acknowledged that there was nothing to prevent prisoners being automatically released until the emergency new law is passed.

The prime minister’s official spokesman would not comment on whether they had identified any terrorists due for release before the new law comes in.

The government has not ruled out derogating – effectively partially suspending – the European Convention on Human Rights in order to apply the new measures, which are likely to be subject to legal challenges.

The Streatham stabbing was the third terror attack in just over two months to be carried out by a convicted terrorist in Britain, following the assaults at Fishmongers’ Hall in London and inside HMP Whitemoor.

Forensic officers outside Boots near where the attack took place (AFP)

Amman, who had previous convictions for cannabis and offensive weapons possession, was initially arrested for planning terror attacks in May 2018, after writing online that he was “armed and ready” and pledging allegiance to Isis.

But he was charged with the lesser offences of collecting and disseminating terrorist material after consultation with prosecutors, and handed a determinate sentence of three years and four months that saw him automatically released on 23 January.

He was being followed by undercover officers when he grabbed a knife from a shop, removed it from its packaging, and started stabbing passers-by in Streatham on Sunday.

Meanwhile, his father, Faraz Khan, has said he never thought his son “would go this far” and he did not know he had become radicalised.

Speaking to Sky News on Tuesday, Mr Khan said Amman was reciting the Koran when they last spoke, a day before the attack, and he had been shocked to learn of his son’s actions.

“He never talked to me about things like that,” he said.

“He said when his mother came to see him she brought him food – that’s the kind of things he talked about.

“I told him not to be naughty, be good, and he listened.”

Scotland Yard said Amman was shot dead by police within a minute of beginning his attack, which was claimed by Isis in a generic statement on Monday morning. Both stabbing victims survived.

Around 50 terrorists are released from prison each year, according to officials, and the figure is expected to be similar in 2020 unless rules change.

Home Office data shows 41 convicted terrorists were released from jail in the year to June, as well as 12 suspects who had been held in custody but not sentenced.

Among those due for release, according to the Henry Jackson Society, is Mohammed Ghani, who threatened to kill police officers, and Britain’s youngest terrorist, who plotted to murder police in Australia.

Also on the list are at least five men who aspired to or travelled to Syria to support Isis, as well as Moinul Abedi, who was jailed in 2002 for stockpiling homemade explosives for a terror attack.