According to The Sunday Times, most of the suspects live in Yorkshire. Their activity is likely to become more active after Labour lawmaker Jo Cox was murdered in June 2016 by a suspected neo-Nazi.
The suspects are under investigation for "proactively plotting" of the attacks by familiarizing themselves with the Islamic institutions and community representatives, the newspaper said.
"The danger far-right extremists pose to national security is no different from Islamist terrorists. They do their research, they identify vulnerable targets and then they make a move. But they are more difficult to track than Islamists because they appear to be much better at operating under the radar. We’re anticipating more problems and attacks by neo-Nazis," a well-informed source said.
In December 2016, National Action, a UK neo-Nazi group which welcomed the murder of Cox, was outlawed in the country.
Cox's murderer, Thomas Mair, was found guilty in November 2016. Earlier media reports in November indicated that Nazi-related materials were found in his home.