ISIS and Al Qaeda are plotting attacks in the UK, the government is expected to warn on Tuesday.
Home Secretary Suella Braverman will describe terrorism by Islamist extremists as “the predominant threat” facing British security in an update to Contest, the UK’s counter-terrorism strategy.
She will say states including Russia pose an increasing threat and are using terrorism to create division in UK society.
There are about 800 live terror investigations in the UK and counter-terrorism police last year made 169 arrests.
Authorities thwarted 39 attacks in the late stages of planning, most of the plots by Islamist extremists.
Two plots were foiled in the past seven months.
Ms Braverman will outline the latest findings in an update to Contest, which has not been refreshed for five years.
The minister will use her speech to draw attention to the acute threat posed by Islamist extremists, The Times reported.
“Islamist terrorism remains the predominant threat,” Ms Braverman will say. “Terrorism is becoming increasingly unpredictable, making cases harder to detect and investigate.”
Ms Braverman will say Islamist terrorism accounts for three quarters of the workload of MI5, the UK’s security service.
Last month it emerged that Iraqi troops had foiled a plot by ISIS members seeking to carry out an attack at a public gathering in Britain.
Gen Abdul Wahab Al Saadi, Iraq’s most senior counter-terrorism officer, said ISIS had been “talking to UK-based terrorists and we know what they are planning”, describing the plot as “a big attack”.
The UK-based extremists were British citizens, he said, and added that western authorities had been informed.
“I can tell you that from the information we found at the site of one of our recent raids the next intended [terrorist] attack will be in the United Kingdom,” he told the Daily Mirror.
The news emerged after Iraqi troops raided a site and killed dozens of militants in the country.
Russia and other countries are using terrorism to create division in the UK and are an increasing threat, Ms Braverman will also warn.
“Terrorist narratives are also exploited by hostile actors such as Russia, which is seeking to promote divisive and polarising narratives in the West. This is likely to increase in the future.”
Russian-linked accounts were used after terrorist attacks such as the Manchester Arena bombing and the London Bridge stabbings to amplify divisive, far-right messaging, research shows.
“This is the first [report] of its kind for five years and is a comprehensive update for the UK’s response to terrorism,” a Whitehall source said.
“It’s about how the fragmentation of [ISIS] and Al Qaeda is now posing a very different threat to our people, while state actors like Russia and Iran will increasingly try to capitalise on terrorism here in the UK.
“We can’t be complacent. The terrorists are morphing and we have to keep our vigilance up.”
UK 'behind the curve' on terror threat
Yvette Cooper, the shadow home secretary, said the UK’s domestic security response was “not keeping up with the fast-changing landscape”.
Speaking at the Royal United Services Institute defence and security think tank on Monday, she recalled how “immense work” was done by British authorities to “build a strong counter-terror response” after the 9/11 attacks in the US and the 7/7 bombings in London.
“We’ve seen the threats change again since then,” she said.
“The UK faces continued challenges from Islamist and far-right extremists radicalised online, in prison or in the community.
“Instability in Afghanistan, Syria and East Africa means that groups affiliated to Al Qaeda and ISIS are operating with greater freedom again.”
Ms Cooper said the Office for Security and Counter Terrorism in the Home Office has “driven progress” in Contest.
“We also need similar progress around the threats, the state threats, state-sponsored, state-backed or state-licensed threats that we can see,” she added.
She also said the government needed to step up to meet new threats posed by advanced technology such as artificial intelligence.
“Hateful extremist online forums, chat groups and algorithms that prey on vulnerable people have been a concern for some time,” she said. “ But generative AI takes that to a new level.”
She referenced to the case of Jaswant Singh Chail, who planned an attack on the late Queen Elizabeth at Windsor Castle on Christmas Day. He claimed he had been encouraged by his “AI girlfriend”.