Offenders who commit antisemitic attacks backed by foreign powers such as Iran will face 14 years in prison under legislation to be included in the king’s speech next week.

Shabana Mahmood, the home secretary, will be given the power under the National Security Act to designate proxy groups, such as those thought to be behind the recent attacks on the Jewish community, as a foreign intelligence service.

Those carrying out activities on behalf of that group will face a maximum punishment of 14 years in jail even if they are unaware of who they are working for.

The move is designed to tackle the growth of foreign proxies recruiting criminals on social media to carry out acts of terrorism, sabotage and espionage.

The number of national security cases involving hostile states carrying out operations such as spying and sabotage in the UK has increased by half in six months, the head of counter-terrorism policing has said.

The move, first disclosed in the Times, comes after the Metropolitan police announced a community protection team of 100 extra officers to help safeguard the Jewish community. The force previously said 300 more officers were needed to tackle the rise in antisemitism across the capital.

The legislation will introduce proscription-like powers for the home secretary to ban state groups such as Iran’s Islamic Revolutionary Guard Corps (IRGC), delivering on a pledge made by Labour three years ago.

The laws will allow police and prosecutors to investigate and prosecute individuals under section 3 of the National Security Act 2023, which criminalises conduct that is likely to assist a foreign intelligence service.

The emergence of proxy groups acting on behalf of Iran and Russia has exploited a gap in Britain’s national security laws.

The law will enable the home secretary to designate Islamist groups such as the Iranian-linked Harakat Ashab al-Yamin al-Islamia, which has claimed responsibility for at least half a dozen antisemitic attacks against Jewish communities.

On Tuesday the prime minister said Iran’s attempts to “foment violence, hatred or division” in British society would not be tolerated as he publicly blamed Tehran for the spate of recent attacks on the Jewish community.

He was speaking as he convened a meeting of leaders from police, prosecutors, the NHS, trade unions, universities and community groups alongside senior ministers to discuss how to combat soaring levels of antisemitism in society.

After the meeting, the Crown Prosecution Service announced guidance instructing prosecutors to fast-track hate crime cases in an attempt to tackle the “deeply troubling rise in antisemitic incidents”.

Since late March, there have been a series of arson attacks at Jewish sites in London, as well as a double stabbing in Golders Green that is being treated as an act of terrorism.

Counter-terrorism police are investigating a suspected arson at a former synagogue in Nelson Street, Whitechapel, in the early hours of Tuesday.

A Met police spokesperson said: “British Jews now appear on the hate lists of every major extremist movement: extreme rightwing groups, Islamist terrorists, elements of the extreme left and hostile state actors.

“It is a deeply concerning convergence, and Jewish communities are living with the consequences of that risk daily.

“This focus does not mean the Metropolitan police is deprioritising other communities. Hate crime in all its forms – including ongoing efforts to tackle racism, anti‑Muslim hate crime, homophobia and other forms of hatred in the capital – remains a core policing priority.”