Terrorists who travel to war zones or plot to kill multiple people will face a minimum of 14 years behind bars under harsh new sentencing guidelines.
New Justice Secretary Dominic Raab said the new powers would deter 'those who kill and maim in the name of warped and fanatical ideologies'.
It is hoped the move will close a potential loophole that has allowed some terrorist plotters to receive shorter sentences.
New Justice Secretary Dominic Raab said the new powers would deter 'those who kill and maim in the name of warped and fanatical ideologies'
The Sentencing Council will today set out its proposed guidance to judges on how they should apply the new mandatory minimum jail term which became law earlier this year.
The Counter-Terrorism and Sentencing Act 2021 created a new category of 'serious terrorist offences' amid concerns offenders convicted of planning attacks were receiving relatively light jail terms.
It stipulated those who are found guilty under the new category should face a minimum of 14 years' custody - with an extension period to be served on licence of between seven and 25 years - unless there are 'exceptional circumstances'.
In its guidance, the Sentencing Council will say it should apply when a court finds there is 'a significant risk' to the public of 'serious harm occasioned by the commission by the offender of further serious terrorism offences'.
It should also cover cases where the offence 'was very likely to result in or contribute to (whether directly or indirectly) the deaths of at least two people' - the so-called 'risk of multiple deaths condition'.
Haider Ahmed, who planned a knife attack similar to the Bridge and Westminster attacks, was jailed for only six years
The proposed guidance will be subject to a consultation which runs to January 11.
Raab said: 'These proposed guidelines will support judges to pass consistent and appropriate sentences in terrorism cases.
'Those who kill and maim in the name of warped and fanatical ideologies will spend longer behind bars, because public protection is our top priority.'
The council's lead member for terrorism offences, Mrs Justice Maura McGowan, said: 'Terrorism offences are serious criminal acts that are constantly evolving, and the law is regularly updated in line with the changing nature of the offences, requiring a new approach to sentencing.
'The council is proposing revisions to existing sentencing guidelines to reflect the new legislation and ensure that the courts have comprehensive and up-to-date guidance for dealing with these extremely serious cases.'
Safaa Boular had her jail sentence reduced to 11 years in 2019 after she was convicted of plotting a terror attack
The Counter-Terrorism and Sentencing Act was drawn up after the 2019 Fishmongers' Hall attack by Usman Khan, who killed two people after being released from prison on licence while serving a sentence for involvement in a plan to set up a terrorist training camp.
The youngest woman to be convicted of plotting a terror attack on British soil had her jail sentence reduced to 11 years in 2019.
Schoolgirl Safaa Boular wanted to become a jihadi bride in Syria, but started plotting an attack in London after the ISIS fighter she planned to marry was killed in an air strike.
The 18-year-old wanted to carry out a grenade and gun attack on the British Museum.
The Court of Appeal later said she was a victim of grooming and lowered her 13-year minimum jail term.
That same year, Haider Ahmed, who planned a knife attack similar to the Bridge and Westminster attacks, was jailed for only six years.
Samata Ullah, a jihadi computer hacker who created a 'one-stop online shop' of information for terrorists from his Cardiff bedroom, was jailed for eight years.