The National Security Bill will create three new criminal offences: planning mass-casualty attacks without ideological motive, creating or sharing extreme violent material, and hostile state-backed activities. It closes a legal gap exposed by the Southport attack and represents one of Parliament’s most significant criminal law changes.
The proposals respond to recommendations made by Jonathan Hall KC, the Independent Reviewer of Terrorism Legislation, after the Southport attack in July 2024. They represent one of the most significant changes to criminal law in this Parliament.
Criminal practitioners, public lawyers, online safety advisers and human rights specialists will all need to track this bill carefully. The proposed offences sit at the intersection of criminal law, free expression and platform regulation. Defence solicitors, prosecutors and in-house teams at tech companies should prepare for new compliance and casework implications.
What is being proposed?
Three main strands have been reported. The first creates a new offence of planning a mass-casualty attack without an ideological motive. This closes what Hall described as a real gap in the law where lone individuals prepare extreme violence outside the terrorism framework.
The second strand targets extreme violent material. Reporting indicates this will cover creating, sharing or possessing content that glorifies serious violence. The third strand introduces measures against hostile state-backed organisations, building on the National Security Act 2023.
The Southport gap in the law
Hall’s independent review in March 2025 found that the existing terrorism definition could not be applied to the Southport attacker because his actions lacked a political, religious, racial or ideological cause. The review identified ten other lone-actor cases with similar features that were not prosecuted as terrorism.
Hall recommended a new offence, adapted from terrorism legislation, where an individual intending to kill two or more people engages in preparation to carry out that intention. He suggested a maximum sentence of life imprisonment. He specifically advised against expanding the terrorism definition itself, warning that this could create unintended restrictions on freedom of expression.
Who does the new offence apply to?
The proposed offence would apply to individuals who take preparatory steps towards mass-casualty violence without an ideological motive. This addresses cases involving extreme personal grievance, fixation or violent fantasy that fall outside the existing Terrorism Act 2000 framework.
Hall told the BBC in 2025 that lone young men were increasingly drawing inspiration from online content presenting extreme violence as a solution. He warned that under current law, even using AI to plan an attack would not meet the threshold for arrest on conspiracy grounds.
What are the human rights concerns?
Hall’s review itself acknowledged the risk that broadening the criminal law in this area could create unacceptable restrictions on freedom of expression. Article 10 of the European Convention on Human Rights protects expression even when offensive or shocking, subject to limitations proportionate to a legitimate aim.
The new offences will be examined for their interaction with Article 10 and Article 8 (private life). Defence practitioners should watch for how preparatory acts are defined, what mental element is required and what safeguards apply to material accessed online but not acted upon.
How does it interact with online safety?
The bill is reported to update the Computer Misuse Act and introduce new offences relating to violent material glorification. This sits alongside the Online Safety Act 2023 regime, which already imposes duties on platforms to address illegal content.
For online safety lawyers and platform compliance teams, the practical question is how the new offences will define extreme violent material, what platform takedown duties will arise and how the new framework interacts with Ofcom’s enforcement powers. The boundaries between protected expression, harmful content and criminal material will need careful drafting in the bill text.
What about hostile state threats?
Reuters has reported that the legislation will include powers targeting hostile state-backed organisations linked to espionage, sabotage or interference. This builds on the National Security Act 2023, which already created offences for foreign interference and the Foreign Influence Registration Scheme.
The new measures are expected to expand the toolkit for proscribing or disrupting state-backed entities operating in the UK. Sanctions specialists, public law practitioners and in-house counsel at organisations with international links should monitor these provisions closely.
When will the bill be published?
The bill text and explanatory notes have not yet been published. The King’s Speech sets out the legislative programme but the detailed provisions will only become clear when the bill is introduced to Parliament. Practitioners should treat current reporting as a guide to direction rather than confirmed law.
The Home Office is expected to lead on the bill. Pre-legislative scrutiny by the relevant select committees and the Joint Committee on Human Rights is likely given the human rights dimensions.
What should practitioners do now?
Criminal defence solicitors should familiarise themselves with the existing Terrorism Act 2000 framework and the gap Hall identified. Online safety and platform lawyers should review existing client compliance arrangements against the likely shape of the new offences. Public law and human rights practitioners should track the bill’s Article 10 implications.
In-house counsel at platforms and at organisations with potential exposure to state-threat measures should brief boards on the proposals and identify likely compliance changes. Firms with relevant practice areas should consider thought leadership and CPD content as the bill progresses.
The proposals are likely to attract significant parliamentary debate. Practitioners with strong views on scope, safeguards or definitions should consider engaging with select committee inquiries and consultation processes once formal documents are published.