Police officers were injured and vehicles damaged when a second major anti-migrant protest turned violent as fears grow over further far-right unrest and disorder across the UK.

Less than 48 hours after masked vigilantes blockaded roads in Dover, around 200 black-clad activists descended on Portsmouth, where a small boat with 140 asylum seekers on board was intercepted off the coast.

In an ensuing standoff with police, some of the protesters, who were trying to stop the newly arrived migrants from being driven away, attacked officers and vehicles.

On Monday, the Home Office strongly condemned the “intimidating and thuggish behaviour”. However, politicians and campaigners raised fears of further unrest across the UK, particularly along the southern coast, with 625 people crossing the English Channel illegally over the past seven days.

Concerns have also been raised that traffickers could be shifting their desired destinations across England’s coast.

Local Patriot groups, thought to be part of a national Patriot Platform network led by Tommy Robinson associate Daniel Thomas, urged their members to be on standby to react to more migrant boats arriving at ports such as Bournemouth, Poole and Portsmouth.

But crime and policing minister Sarah Jones vowed "disorder of any kind will never be tolerated”, warning that crossing the line from a "peaceful protest into illegality will face the full force of the law”.

Giving a statement in the Commons on Monday afternoon, she said: “Peaceful protest is a fundamental part of our democracy, and it must be defended. But so too is the right of other citizens to go about their lives without undue interference, and there can be no excuse for threatening behaviour or serious disruption.

“Let me therefore make clear to the House and to the country that disorder of any kind will never be tolerated ... illegality will face the full force of the law.”

But she added: “None of this is to in any way minimise the very valid concerns that people have when they see vile criminal gangs exploiting our nation's generosity and people making illegal and unnecessary journeys to reach this country."

It comes after Nick Lowles, chief executive of anti-racism charity HOPE, said any failings to act on threats of mobilisation could mean “things will only get worse from here”. The group later warned that the events should be a “wake-up call for authorities to take this type of threat seriously”.

Lord Walney, who was Keir Starmer’s Independent Adviser on Political Violence and Disruption, told that the protest in Portsmouth highlighted the need for police and political leaders to “respond firmly”. He said: “Politicians who excuse extreme protestors of either right or left because they sympathise with the cause risk fanning a wave of unrest and disorder across the UK.”

Reform UK leader Nigel Farage said the country was “on the edge of serious civil disturbance”, warning the movement of small boats across the Channel was getting out of control. “I predicted an invasion, and boy is it happening,” he said.

However, he said protesters dressed in paramilitary-style uniforms were not going to solve the issue.

So far this year, 16,513 people have been detected crossing the English Channel in small boats, which is the lowest for five years when the same figure at this point in 2021 was 12,647.

On Monday afternoon, a press conference arranged by Reform UK home affairs spokesman Zia Yusuf on the coast in Portsmouth was interrupted by Mr Thomas, a leading figure behind the protest in Dover.

Mr Thomas said there was no violence in Dover and, when questioned about his Patriot Platform group’s masks and attire being intimidating, said: “The reason people felt potentially intimidated was because of the faces covered. I’ve made that point very clear. The only reason they’ve done that is because no one wants to be labelled far right.”

He claimed the group members were creating an “infrastructure of men” to create a voting bloc to back “the most suitable party that is able to bring this country back into order”.

Across both incidents in Dover and Portsmouth at the weekend, neither Kent nor Hampshire and Isle of Wight forces made any arrests. However, an investigation has been launched to identify those who attacked officers and vehicles in Portsmouth.

Footage shared on social media from Sunday night showed protesters blocking roads in an attempt to stop the migrants being taken by coach to Kent. Mr Thomas, also known as Danny Tommo, livestreamed himself running on the beach toward the coaches, threatening those preparing to help the migrants: “If you don’t stop right now I’m calling 1,000 men to come to this place.”

The migrants’ dinghy was met by lifeboats from the Isle of Wight when it reached UK waters, having set off from the Cherbourg area. It is thought to have made one of the longest journeys of any small boat, and landings as far west as Hampshire are rare.

It is understood that the government currently has no evidence to suggest there has been a change in people smuggler tactics.

However, Mihnea Cuibus, senior researcher at the University of Oxford’s Migration Observatory, said people traffickers could change targeted landings along England’s southern coast to avoid the patrolled Calais to Dover route.

“It’s much harder to leave by boat from around the Calais area because of all of the patrols, drones in the air, and more boots on the ground, so they're just trying to find ways to avoid that,” he told .

Donna Jones, Conservative police and crime commissioner for Hampshire and Isle of Wight, said that places such as Portsmouth are “not set up” for the arrival of migrants. Portsmouth’s Liberal Democrat council leader Steve Pitt said the city was an “unsuitable” disembarking location for the boats.

A Home Office spokesperson said: “The right to peaceful protest is fundamental to our democracy, but it must never cross a line into disorder. We thank the emergency services who safely managed this situation.

“This government is doing the hard and necessary work of bearing down on small boat crossings, with the lowest number of June to August arrivals since 2020.”