Contemporary Britain is battling far-right rhetoric similar to that which divided the country in the 1970s, with the Brexit debate revealing how politicians continue to stoke racial tension, according to the director of a film about the formation of Rock Against Racism (RAR).

Rubika Shah, the director of a new documentary about the lead up to RAR’s march and concert in east London’s on 30 April 1978, says the UK is still struggling to counter the far-right populism that made the National Front a force in the 1970s.

“There are so many similarities,” Shah said. “I hope people look at some of the stuff that was happening in the late 70s and think: ‘Wow, this is actually happening now.’”

White Riot follows the founder of RAR Red Saunders and the close-knit group of organisers who arranged the march and concert that brought 100,000 people from around the UK to Victoria Park in Tower Hamlets, where the National Front had won almost 20% of the vote in recent elections.

Shah said she deliberately included National Front slogans such as “It’s our country, let’s win it back” to show their echoes in modern campaigning, such as Dominic Cummings’ “Take back control” mantra that was used during the Brexit referendum. “It’s scary how that language creeps back in,” she said.

The director said she was shocked to hear Boris Johnson use the term “invisible mugger” to describe the Coronavirus, as “mugger” was a word used by the National Front and right-wing media to describe black people in the 1970s.

“It’s from people who would have been fairly young at that time,” she added. “So whether it is deep seated in their subconscious or if they’re actually going out of their way to use that language because it evokes what was going on in the late 70s, one would wonder.”

RAR was formed as a reaction to racism in 1970s media reports and a spate of incidents where high-profile musicians voiced far-right ideas or support for politicians who campaigned for deportation of black and minority ethnic Britons.

In April 1976, David Bowie told reporters that the UK was ready for a fascist leader, and Rod Stewart said there were “too many immigrants” in Britain, shortly after he emigrated to America. The most infamous was Eric Clapton, who while on stage at the Birmingham Odeon in August 1976, declared that Britain was becoming a “black colony” and that he wanted “the foreigners out”.

Mykaell Riley of Steel Pulse – the Birmingham roots reggae group who shared the RAR stage with X-Ray Spex, Tom Robinson Band and The Clash in 1978 – said there was disbelief at first that either Bowie or Clapton, who took inspiration from African-American blues guitarists and had just covered Bob Marley’s I Shot The Sheriff, were flirting with racism.

“There was absolute disbelief,” said Riley. “He’d just covered Bob Marley, we just thought it was the press having a go at ‘dear old Eric’. The Clapton rant just underlined a particular mindset in – not just the musical landscape – but Britain itself.”

He added that when the band first heard of RAR, who released fanzines and organised nationwide gigs that featured black and white artists, they didn’t think the idea was that original. “Most of our audience were punks, we were already doing that work,” said Riley. “We would go to gigs armed on occasions because it was normal for us to end up in a ruck with our own audience.”

Riley believes it would be hard to emulate the event in modern Britain because online activism has taken over as the dominant form of dissent. “RAR called for people to come out and support and people did in their thousands,” said Riley. “It’s very different when you click, and that’s it. It’s so easy now to engage and just as easy to disengage.”

Shah and Riley believe the legacy of RAR can be seen in the popularity of the Extinction Rebellion mass protests to popularise the fight against climate change, and think thousands of Britons would be protesting about the treatment of NHS workers during the Covid-19 outbreak, if it were possible.

“If we were able to protest at the moment there would probably be a big protest for the NHS,” says Shah. “Some of the things that are going on in that regard are just shocking.”

• White Riot will be live streamed from 8.30pm on Thursday 30 April on Curzon Home Cinema (with a Q&A that follows). It will then be available until Monday 4 May and is due to be released in cinemas this September.