The number of far-right prisoners convicted for terror offences in Great Britain climbed by a third last year to their highest recorded level, and accounts for more than one in six of all terrorists held in prison, according to official figures. Labour said the disclosure underlined the “dangerous threat” posed by the far right, which comes after last weekend’s counter-demonstration in Westminster where more than 100 were arrested following violent clashes. The Home Office data shows that 44 “extreme rightwing” prisoners were in custody for terror offences across Great Britain, up from 33 a year ago. Three years ago, the figure was nine and no higher than five before that. Those who have been jailed in recent years include Thomas Mair, who murdered Jo Cox four years ago this week, and a neo-Nazi who plotted to kill another Labour MP, Rosie Cooper, with a machete a year later. Islamist extremists still form the largest category of terror prisoners, but at 183 last year the overall number has remained roughly flat since 2018 – meaning the proportion of far-right terror prisoners has increased to a record 18%. Conor McGinn MP, the shadow security minister, said: “This significant rise shows the very serious and dangerous nature of far-right extremism”. He called on ministers to act swiftly to tackle the growing threat. The opposition MP wants the Home Office to restart urgently its review of its Prevent counter-extremism strategy, which stalled after its first chair, Lord Carlile, was forced to step down last December. “We need a comprehensive, focused strategy,” McGinn added. Several thousand people gathered in Parliament Square, central London, last Saturday as part of a far-right “unity demonstration” attended by extremist groups such as Britain First, the largest mobilisation of the far right seen on the streets of London since 2017, according to the anti-fascist group Hope Not Hate. The protest came in response to the daubing of a statue of Winston Churchill with graffiti a week earlier during a Black Lives Matter protest. Experts fear that it could herald further reactivation of the far right. Joe Mulhall, from Hope Not Hate, said: “This could represent a new chapter where the far right focuses on black communities, on immigrants and on crime as they did before 9/11. “But what’s different this time is that it is so much easier for young people to access far-right terrorist material online through social media channels such as Telegram – and follow coverage of attacks that take place around the world.” The numbers of far-right extremists jailed in Britain have increased after ministers banned National Action towards the end of 2016, the first time a far-right group has been proscribed since the second world war. Since then, the far right in the UK has splintered and increasingly involves less formal organisation operating through a loose network of internet forums in an attempt to evade prosecution, although this is not always successful. Four National Action “die-hards” were sentenced in Birmingham last week after being found guilty of being active members of the group. Mark Jones, a key figure in the group, was jailed for five years and six months after knives and Nazi paraphernalia were found at his home, while his partner, Alice Cutter, who had once entered a “Miss Hitler” beauty contest, was jailed for three years. A Home Office spokesperson said it was commited to tackling all forms of terrorism. “We must never be complacent and we are giving the police the tools they need to protect us, such as increasing funding for counter terror policing by £90m this year and creating new powers and tougher sentences via the counter terrorism and sentencing bill,” they added.