Brexit referendum aftermath sees 'rise in extremism'
Political extremism has increased since the 2016 Brexit referendum, the head of terrorism investigations in the North West has told BBC Radio Manchester.
Det Supt Will Chatterton said dealing with far-right extremism was a real challenge, with "open hostility" towards politicians.
He said the unit's cases included "horrific sentiments" posted online.
The Home Office said it was "committed to stamping out extremism in all its forms".
Det Supt Chatterton said Brexit was "a very emotive issue". "Unfortunately people will sometimes vent their frustration against politicians," he said.
"With Brexit we are seeing an increase in right-wing activity.
"You can see politicians are worried and you see the open hostility sometimes against politicians.
"Sadly, Jo Cox was murdered at the hands of someone that counter terrorism ended up investigating. It's a real challenge.
"Most recently we uncovered and disrupted a plot to try to kill a serving MP."
In May, Jack Renshaw was jailed for life over a plan to murder Labour MP Rosie Cooper.
The trial at the Old Bailey heard he was radicalised as a teenager after joining the English Defence League and then the British National Party, but there was no evidence that Brexit played a part.
Security minister, Ben Wallace, said: "The growth of the far-right is not a 'local British' problem linked to Brexit, but a global problem that our partners in Europe, the US, Canada, Australia and New Zealand are tackling.
"We take the security of Members of Parliament extremely seriously, and violence is never acceptable in a stable democracy like ours."
Det Supt Chatterton said there are more than 700 live counter-terror investigations in the UK.
While a large proportion of the cases were linked to international terrorism, he said the number of far-right investigations in general was "significant".
He said: "We deal with terrorism right across the spectrum, whether that is left-wing terrorism, right-wing terrorism, whether it is terrorism on an international footing.
"We deal with terrorism of all shapes and sizes.
"We are facing an unprecedented demand at the moment and that has been rising over the last few years."