"Whilst the investigation remains ongoing, at this time there is nothing to suggest there is any threat to wider public safety in relation to this matter," the force said in a statement.
The force did not reveal which neo-Nazi group he was accused of belonging to, though there are only two far-right extremist groups in the UK banned under terror law.
National Action was banned in 2016 while its splinter group the Sonnenkrieg Division - described by anti-racism charity Hope Not Hate as a "Nazi Satanist" group - was banned last week by Home Secretary Priti Patel.
Anyone convicted of being a member of, or offering support to, banned terrorist groups faces up to ten years in prison.
