Far-right extremists could exploit tensions around Brexit, the UK’s counter-terror chief has warned.

Police foiled 18 terror plots since March 2017, four of which were far-right, Metropolitan Police assistant commissioner Neil Basu said.

Basu warned a no-deal Brexit would be “very bad” for policing and said right-wing terrorism was a concern, but that forces would be working hard to stop the “drift” to far-right incidents.

He told the BBC that a spike in hate crime witnessed after the EU referendum in 2016 has “never really receded”.

“So there’s always a possibility people are being radicalised by the kind of febrile atmosphere we’re seeing at the moment,” he said.

While there is no intelligence indicating an increased potential for attacks post-Brexit, Basu said: “What’s most concerning me… is its potential to divide communities and set communities against each other.”

It comes as more than one in five of calls from the public made to the police led to a “significant piece of intelligence” which help thwart a plot, the police chief said.

More than 31,000 pieces of information were passed to police in 2017, which more than halved to 13,093 in 2018.

A record 700 terror investigations are ongoing, up from 500 in 2017.

Police have launched an ad campaign to encourage people to report suspicious activity.

The 60-second film, which shows a man stockpiling containers of hazardous materials out in public, will be played across 120 UK cinemas from January 25.