Britain faces the threat of a murderous terror attack from a Far Right extremist similar to the mass murderer Anders Breivik who gunned down 77 young Norweigans, the Security Minister warned today.

James Brokenshire accused groups such as the English Defence League (EDL) of inflaming tensions on the streets, claiming that their messages of “hate-filled prejudice” could “stoke radicalisation” among unstable loners motivated by race hate.

He disclosed that one in ten cases referred to a Home Office scheme to stop youngsters being caught up in terrorism related to the Far Right.

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Seventeen right-wing extremists are serving prison sentences linked to terrorism, including a man who built up the biggest arms cache uncovered recently in Britain, two men convicted of preparing to use home-made poison in an attack and another jailed for circulating terrorist literature.

“Any of these examples could have proved deadly,” Mr Brokenshire told the International Centre for the Study of Radicalisation and Political Violence in London.

“All these cases are, without exception, self-starting groups and individuals, rather than part of a centrally-directed terrorist organisation. The Far Right threat is not as widespread or systematic as the al-Qa’ida inspired threat and operationally there are vast differences.

“But we also notice that at the same time, at its core, the Far Right appeals to people who share many of the same vulnerabilities as those exploited by al-Qa’ida inspired extremism.

“It feeds off the same sense of alienation and questions around identity and it has the same ambition to reshape the world in an impossible way. The threat is real, and our response must be effective.”

Mr Brokenshire condemned the “worrying phenomenon” of groups like the EDL promoting “offensive, anti-Muslim messages”, adding: “They are divisive and run contrary to the values of respect and tolerance of different faiths and beliefs.”

It was believed “so-called defence leagues” can provide “gateway ideologies” which enable sympathisers to graduate to hardline extremist activity, the Minister said.

Mr Brokenshire said the Home Office counter-terrorism strategy had been updated 18 months ago to include the activities of the Far Right and said ministers were consulting other European governments over how to deal with the threat.

Thousands of staff in schools, prisons, social services and hospitals are being trained to spot individuals who are drifting towards extremist views of all kinds, he said.