File picture of an anti-mosque demonstration in Bolton in November 2016. National Action became the first extreme right-wing group to be banned in Britain in DecemberCredit:Joel Goodman/LNP Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. “This will mean that being a member of, or inviting support for, this organisation will be a criminal offence.”National Action is a racist, anti-Semitic and homophobic organisation which stirs up hatred, glorifies violence and promotes a vile ideology, and I will not stand for it.”It has absolutely no place in a Britain that works for everyone.”How National Action endorsed the murder of Labour MP Jo CoxAfter the murder of Labour MP Jo Cox in June 2016, National Action endorsed her killing.The group posted a message, which read: “Our thoughts go out to Thomas Mair #Britain-First #JoCoxMP’ and, ‘Don’t let this man’s sacrifice go in vain. #JoCox would have filled Yorkshire with more subhumans.”Thomas Mair was jailed for life after being found guilty of murdering the politician. “These arrests are the consequence of a Home Office Police Force led operation supported by the Army. This is now the subject of a civilian police investigation and it would be inappropriate to comment further.”What is National Action?National Action became first extreme right-wing group to be banned under terrorism laws in December 2016.The proscription meant that being a member of or inviting support for the organisation is a criminal offence carrying a sentence of up to ten years’ imprisonment.An entry for National Action in the official list of proscribed groups says it is a “racist neo-Nazi group” that was established in 2013 and has branches across the UK which “conduct provocative street demonstrations and stunts aimed at intimidating local communities”. The arrests were carried out by police in conjunction with counter-terror units from the West Midlands, Wales and the East Midlands.Several properties are being searched in connection with the arrests.A police spokesman added: “The arrests were pre-planned and intelligence-led; there was no threat to the public’s safety.”An Army spokesman said: “We can confirm that a number of serving members of the Army have been arrested under the Terrorism Act for being associated with a proscribed far right group. Jo Cox was murdered by far-Right fanatic Thomas Mair, right, in June 2016Credit:PA Serving British soldiers are among four alleged members of National Action, the banned neo-Nazi group, arrested on suspicion of preparing acts of terrorism.The men – a 22-year-old from Birmingham, a 32-year-old from Powys, a 24-year-old from Ipswich and a 24-year-old from Northampton – were held on Tuesday.The Ministry of Defence confirmed that “a number of serving members of the Army have been arrested under the Terrorism Act”.West Midlands Police said the four men have been arrested on suspicion of terrorism offences.A spokesman said they “have been arrested on suspicion of being concerned in the commission, preparation and instigation of acts of terrorism under Section 41 of the Terrorism Act 2000; namely on suspicion of being a member of a proscribed organisation (National Action) contrary to sec 11 of the Terrorism Act”.All four men are being held at a police station in the West Midlands. The document adds that the group is “virulently racist, anti-Semitic and homophobic”.Its activities and propaganda materials are particularly aimed at recruiting young people, according to the list.What the Home Secretary has said about National ActionAnnouncing the move to ban National Action, Home Secretary Amber Rudd described the group as a”racist, anti-Semitic and homophobic organisation”. She said:”As Home Secretary, I am clear that the safety and security of our families, communities and country comes first.”So today I am taking action to proscribe the neo-Nazi group National Action. The flag of National Action, which was established in 2013Credit:Joel Goodman/LNP The phrase “Death to traitors, freedom for Britain”, which was said by Mair in court, appears alongside the listing for National Action’s website on Google.In the wake of Mair’s conviction, warnings emerged that the terror threat from the extreme Right could be growing.