The number of right-wing extremists behind bars in Britain has more than doubled in four years.

In 2022, 59 prisoners (26%) were classed as holding “extreme right-wing” views, up from 52 (23%) the previous year.

This is more than twice as many as the 28 recorded in 2018 and a new record high since records began in 2013, Home Office figures show.

While the “vast majority” (66%) are still classed as having Islamist extremist views, the number of inmates recorded as holding this ideology fell from 154 to 149 in the 12-month period.

The figures also reveal the number of children arrested for terrorism activity has risen to its highest level on record.

Of the 166 total arrests made in 2022, 32 (19%) were under 18, up from 20 out of 185 arrests (11%) in 2021.

While this was the highest proportion seen in an annual period, it was largely a result of falls in arrests of those in older age-groups, a Home Office report said.

The number of suspects arrested who were aged 18 to 20 also rose from 17 to 28. Those aged 30 and over continued to account for most arrests.

Overall, the number of people arrested over terrorism activity fell 10% to 166, the lowest since 2010 (127).

In the wake of a review into the Government’s anti-terror programme, Prevent, Home Secretary Suella Braverman last month said the threat from right-wing extremism “must not be minimised. It is serious and it is growing.”

She said it must be “robustly addressed” but is “not the same either in nature or scale as the threat from Islamism”.

In November, MI5 director general Ken McCallum described extreme right-wing terrorism as now a “diffuse online threat”, adding: “From the comfort of their bedrooms, individuals are easily able to access right-wing extremist spaces, network with each other and move towards a radical mindset.”

Schoolboys account for the highest proportion of people considered to be most at risk of radicalisation by Prevent and schools are making the highest number of referrals to the scheme for the first time, according to previously published figures.

A Home Office assessment from June 2021 found the extreme right-wing threat “is likely to increase over the next five years, with economic decline caused by Covid-19 being a likely driver of increased threat”.