About 40 neo-Nazis are being investigated by police amid fears that they are plotting terrorist attacks against Muslims around the country.

The extremists are understood to be operating in “far-right hotspots” predominantly in Yorkshire, including Leeds, Dewsbury and Batley, according to police intelligence sources familiar with the investigations.

They believe the threat from the far right has increased over the past year, since the murder of the Labour MP Jo Cox by a neo-Nazi. Thomas Mair, the white supremacist who killed Cox in Birstall, West Yorkshire, in June last year was not known to police. He was jailed for life.

The neo-Nazis being investigated are “proactively plotting” by familiarising themselves with Islamic institutions and community representatives.

This contrasts with those who carry out hate crimes