The chief constable of the Police Service of Northern Ireland has warned that the return of a hard border in the event of a no-deal Brexit could revive paramilitary groups.

It could become a “trigger and a fuelling point” for more people to join extremist groups, Simon Byrne told the BBC Radio 4 Today programme on Thursday. He said: “If we get this wrong we could drift back to almost a paramilitary style of policing.”

The chief constable also said Northern Ireland’s political vacuum and uncertainty was becoming a “breeding ground for dissident hate” and expressed concern at the “tempo and pace” of dissident republican attacks.

He made the stark assessment after fresh violence this week.

A man in his 40s was shot in the legs on Wednesday night in what police called a “paramilitary-style” shooting. The attack happened in the Ardoyne, a republican stronghold in north Belfast. He was being treated at hospital.

On Monday night Malcolm McKeown, a 54-year-old career criminal with loyalist paramilitary links, was shot up to six times while sitting in his BMW at a service station in Waringstown, County Down. Detectives investigating the murder have arrested two men aged 28 and 30.

In a separate incident earlier on Monday, security forces escaped injury after being “lured” to a bomb that exploded in County Fermanagh close to the border with Ireland. There were no casualties.

Byrne told the BBC that the Continuity IRA, a previously dormant dissident republican group, had come back to the fore and “are clearly intent on murdering one of my officers”.

The chief constable said the PSNI had no intelligence that the UK’s departure from the European Union was directly fuelling paramilitary groups but said “speculation around different forms of Brexit” plus Northern Ireland’s political vacuum were heightening tension.

Talks in recent months between Sinn Féin, the Democratic Unionist party (DUP) and other parties have so far failed to revive power sharing at the Stormont assembly, which has been mothballed since January 2017.

Byrne also said there was a “a strong clamour” for more officers on the beat – a call likely to swell if the PSNI are asked to monitor the estimated 300 border crossings between Northern Ireland and the Republic of Ireland.

The former Cheshire police chief constable took over policing in Northern Ireland in July – just in time for the marching season and the 50th anniversary of the start of the Troubles. He has made several warnings that a hard Brexit would damage the peace process.