The UK's interior ministry announced on Thursday that the country's terrorism threat level had been raised to "severe", the second highest in the five-tier system, after two Jewish men were stabbed following a string of arson attacks on Jewish sites.
That threat level indicates another attack "is highly likely in the next six months". It had been at substantial — meaning an attack was "likely" — since February 2022.
The government will also introduce new legislation to tackle state-sponsored threats, amid warnings that states such as Iran were using criminal proxies.
Ministers said the government would fast-track legislation allowing the prosecution of people acting as proxies of a state-sponsored group, so they can be dealt with in the same way as spies for foreign intelligence services.
British police and security officials have warned that Iran has increasingly sought to use criminal proxies to carry out hostile activity, and that Russia and China have done the same.
A pro-Iranian government group has claimed responsibility for some recent attacks.
the interior ministry announced the country's terrorism threat level had been raised to "severe", the second highest in the five-tier system and meaning another attack "is highly likely in the next six months".
In March, two men were charged under the UK's existing National Security Act with being tasked by Iran to carry out hostile surveillance, and in 2025 three men were convicted of an arson attack on Ukraine-linked businesses.
Officials say Moscow turned to criminals or those with existing grievances following the expulsion of Russian spies over the 2018 poisoning of Russian double agent Sergei Skripal.
Such accusations have been rejected by Moscow, Beijing and Tehran, which say they are politically motivated.
Thursday's announcement of new powers, and additional funding for security, follows criticism of Britain from Jewish community leaders and the Israeli government after a spate of recent attacks, mostly arson, on Jewish targets in London.
The recent incidents are part of a rising number of antisemitic attacks in the UK and worldwide since the October 2023 Hamas assault on Israel that triggered the war in Gaza.
Jewish leaders in the UK have said regular, large marches in support of Gaza have created a more hostile environment in the capital, where they say anti-Semitism is increasingly common.
In October 2025, two people were killed after an attack at a synagogue in the northern English city of Manchester.
A week later, two men went on trial over a plot to kill hundreds in a gun rampage, inspired by the self-proclaimed Islamic State group, against the Jewish community.
They were found guilty in December, just more than a week after a mass shooting at a Jewish Hanukkah celebration at Sydney's Bondi Beach.
The UK's independent reviewer of terrorism legislation, Jonathan Hall, told the BBC the British attacks had become "the biggest national security emergency" since 2017, when there was a string of high-profile attacks.
Interior minister Shabana Mahmood said $47 million in additional funding would pay for more protective security for the country's synagogues, schools, places of worship and community centres, boosting police numbers in areas with a large Jewish community.
"We are seeing a huge increase in antisemitism, and that's why the government's work on education and stamping out antisemitism across other parts of the public sector is also an incredibly important part of this picture," Mahmood said.
She did not say the legislation would be used against the Islamic Revolutionary Guard Corps, but told Sky News: "I expect to be making decisions in the very near future about the groups that we will be designating as state-linked."
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