Extreme right-wing terrorism is being fuelled by hate spread online, a campaign group has warned.
The report by Hope not Hate says further violence from the far-right and claims supporters of the outlawed National Action group are subverting government bans by operating under a new front.
The anti-fascist organisation is calling for the Government and police to do more to crack down on the "peddlers of hate" spreading their message on social media.
The warning comes after Britain's most senior counter-terror officer Assistant Commissioner Mark Rowley revealed four extreme right-wing attack plots were foiled last year.
"We are facing a surging threat from far-right terrorism and violent extremism," said Hope not Hate chief executive Nick Lowles.
"Combined with burgeoning online hatred, directed particularly towards Muslims, we fear further violence from the extreme right in the months to come.
"This rising terrorist threat is the consequence of the increasingly confrontational tone of online far-right rhetoric, combined with the almost universal extreme-right belief that a civil war between Islam and the West is coming, as well as the growing influence of hard-line European Nazis living in the UK."
The annual "State of Hate" report, published on Friday, profiles right-wing groups in the UK and argues that far-right inspired extremism is on the rise, despite the collapse of support for British groups such as the BNP.
It warns of a growing extreme right-wing hatred online, highlighting the case of Finsbury Park Mosque terror attacker Darren Osborne, 48.
He was jailed for at least 43 years after ploughing a hire van into a group of Muslims after becoming radicalised by far-right material within just a few weeks, his trial heard.
Mr Lowles added: "No-one should be surprised by this upsurge - we have long warned the authorities about the problem of far-right terrorism and violence -and it is vitally important now that police and the Government do more to crack down on the peddlers of hate and those pushing a civil war rhetoric."
Security Minister Ben Wallace said: "This Government did not hesitate to proscribe a neo-Nazi group, National Action, when the evidence was enough and we will not hesitate to take further action.
"We have continued to enforce this by proscribing National Action's known aliases Scottish Dawn and NS131 as well.
"Through our Prevent strategy, we are successfully fighting back against the terrorist recruiters and safeguarding vulnerable people who are being preyed upon - whether by Islamists, neo-Nazis or other violent extremists.
"At its heart this report shines a light on the growth of intolerance across the UK and Europe and we should all take a stand against extremism whether it is expressed by far right, Islamist groups or other movements."