The former head of counter-terrorism for the UK's Metropolitan Police has warned of a growing threat from right-wing extremists in the country.

Sir Mark Rowley says extreme right-wing groups are operating in similar ways to Islamist extremists in the UK, citing figures that of 14 terror plots foiled in the country last year, 10 were from Islamic extremists, and four were from right-wing extremists.

Sir Mark said despite the growing threat, some government institutions and media were underestimating the risk.

"For the first time since the second world war we have a domestic, proscribed terrorist group, it's right-wing, it's neo-Nazi, it's proudly white supremacist, portraying a violent, wicked ideology," Sir Mark told the BBC.

"I don't think we've woken up to it enough.

"Now I'm not going to say it is the same level of threat as the Islamist threat … but it's very significant and it's growing and what I've seen over the last number of years is a lack of recognition of that."

Sir Mark Rowley was the Metropolitan police's anti-terrorism chief between 2014 and 2018. ( Reuters: Peter Nicholls )

BBC Newsnight reported neo-Nazi group National Action had been at the forefront of aggressive, right-wing extremism in Britain.

The white supremacist organisation, which uses Nazi iconography in its propaganda material as well as quotes from Adolf Hitler, was the first far-right group to be banned under UK terrorism laws in 2016.

The group celebrated the murder of UK Labor MP Jo Cox in 2016 and has produced material providing tactical advice on how to sow tension and discord in communities, as well as how to avoid police surveillance.

It is now a criminal offence in the UK to be a member of the organisation, but National Action was linked to at least two foiled terror plots last year.

In June, an alleged member of National Action, 23-year-old Jack Renshaw, pleaded guilty to preparing an act of terrorism by buying a machete to kill Labor MP Rosie Cooper last year.

And in July, National Action member Jack Coulson was sentenced to four years and eight months in prison on terrorism charges related to his possession of a guide on how to create hazardous devices. The 19-year-old had previously boasted of wanting to shoot Jewish MP Luciana Berger in the head.

In September last year, three men, including two serving soldiers, were charged with terrorism offences including allegedly belonging to National Action.

Sir Mark said the UK's police, security services, Home Office, Home Secretary and the Prime Minister, Theresa May, spoke frequently about the growing threat of right-wing extremism, but wider government institutions, media and the community were underestimating the risk.

"If we sleepwalk into it, then I think there is a real danger we give them more scope to get stronger," he said.

"They're repackaging their aggressive intolerance and sometimes thinly disguised advocation of violence, they're repackaging that and attaching it to mainstream political debate.

"That's not quite the same as mainstreaming, but what it does mean is collectively we need to be alert to that whatever leadership or political or journalistic position we are in, and try and guard against it.

"Otherwise what we are doing is letting these extremist groups infiltrate mainstream politics and generate credibility which then lets them present themselves as representatives of 'white Britain' or 'Muslim Britain' — which they certainly aren't."

In another right-wing terror plot foiled last year, Neo-Nazi Ethan Stables planned to carry out an attack on a Cumbria pub which was holding a gay pride night. He was sentenced to an indefinite hospital order in February.

Former home secretary Amber Rudd has described National Action as a "vile group" who promote homophobia, violence and terrorism, which "have no place in this country".