The number of right-wing extremists held behind bars under terror laws reached the highest on record in 2018, according to new Home Office figures.
The number increased from six in 2016 to 10 in 2017, and then jumped to 28 last year and now stands at 33.
The rise coincides with another decrease in the number of Islamist extremists held, which dropped for the second year running.
The number of Islamic extremists peaked in 2017, with 185 people in prison or on remand for terror-related offences.
However, since then, this number dropped to 178 in 2018, and again to 171 in 2019.
The overall number of arrests made for suspected terrorist activity has continued on a downward trend.
There were 266 arrests in the past year, with 23 per cent being released without charge - the lowest percentage since records began after the September 11 terror attacks in 2001.
Previously, over 2017/18 there were 354 arrests and nearly half - 48 per cent - of all those arrested were released without charge.
Security minister Brandon Lewis said the government “will never be complacent” when it comes to terrorism.
"These statistics show just one part of the breadth of work undertaken by the government, police, security and intelligence agencies and local authorities to reduce the terrorist threat," he said.
"From arrests and prosecutions to safeguarding and early intervention through our Prevent programme, we will continue to do what it takes to keep the public safe."