One in three terror suspects arrested in Britain last year was white.
Official figures show that 91 out of a total 260 individuals held on suspicion of terrorism-related offences were white.
This was 20 higher than in 2015, and the highest tally for a calendar year since 2003.
It means 35% of all those held were of white ethnicity in 2016, up from 25% in the previous 12 months.
It was the only ethnic group to record a rise last year, Home Office figures show. The sharpest fall was for those of Asian ethnic appearance, down by 24 to 125.
Statistics on individuals' ethnicity are not broken down by type of suspected extremism.
The number of people arrested for suspected international terrorism fell by 10%, from 225 to 203, although the majority of arrests are still in that bracket.
The category refers to activity linked to or motivated by any terrorist group that is based outside the UK which operates in and from third countries.
By contrast, arrests for "domestic" terrorism more than doubled from 15 to 35, accounting for around one in eight arrests.
Domestic terrorism refers to activity where there are no links to either Northern Ireland-related or international terrorism.
The figures are not broken down further but the disclosure comes amid mounting concern over far-right extremism.
Authorities warned there were signs that the threat could be growing following the conviction of Thomas Mair for the murder of Labour MP Jo Cox.
The Government's Prevent and Channel programmes are handling a rising number of referrals linked to far-right extremism.
Counter-terrorism police have said that, while the threat is not of the same gravity as that posed by Islamic State or al Qaida, there are extreme right-wing groups attempting to provoke violence and sow discord.
Shashank Joshi, a senior research fellow at the Royal United Services Institute (RUSI) security think tank, said: "It's clear that there is a growing challenge from far-right extremist individuals and groups.
"At the last count, one in ten Prevent referrals and one in four Channel referrals were linked to the far-right."
He cautioned against drawing strong conclusions from the arrest figures as they are based on relatively small numbers.
Meanwhile, it was also revealed that the number of people stopped at ports, airports and international rail stations under counter-terrorism powers fell by almost a third last year.
Schedule 7 of the Terrorism Act 2000, which allows officers to question individuals entering or leaving the country, can be used to determine whether the person in question appears to be concerned in the commission, preparation and instigation of acts of terrorism.
In the year to the end of December, a total of 19,355 people were examined under the power in Britain.
This was a 30% drop compared with 2015, when 27,530 stops were made, while the number had fallen from more than 85,000 in 2009/10.
Reasons cited for the decline in stops included improved capturing of passenger data and better use of targeting techniques.
The total tally of arrests, 260, was down by 8% on 2015, but remained high compared to other years.
Earlier this week it was revealed that UK security services had foiled 13 potential attacks in less than four years, while counter-terror units were running more than 500 investigations at any time.
The official threat level for international terrorism has been at severe, meaning an attack is "highly likely", for more than two years.
Security minister Ben Wallace said: "We are determined to detect, disrupt and where possible prosecute all those who pose a threat to the UK.
"The figures released today once again highlight the hard work carried out by the police, Security Service and Crown Prosecution Service day in and day out to keep the people of this country safe."