Sir Keir Starmer issued a stark warning to racist, far-right thugs rampaging across British cities, “guaranteeing” that they would face swift justice and “the full force of the law.”

In a tough statement to the nation, the Prime Minister told those responsible for the horrific events in Hull, Halifax, Liverpool, London, Southport and Rotherham: “I guarantee you, you will regret it.” More than 100 people were arrested following the violent riots on Saturday.

The Prime Minister made her powerful statement as a mob stormed a hotel in Rotherham housing asylum seekers awaiting hearings on their claims. Despite knowing there were people inside, local residents set fire to the hotel.

On Sunday afternoon, violent thugs wearing balaclavas and carrying St George’s flags threw chairs at police and set off fire extinguishers outside the Holiday Inn Express in Manvers, a suburb of Rotherham in South Yorkshire. The anti-immigration hooligans chanted “get them out”, “you’re not welcome here anymore” and “Yorkshire” as they egged each other on to attack the hotel.

Another group of young men held a banner reading “Stopping the boats means stopping the stabbings” and shouted other offensive slogans against Muslims and immigrants. The group smashed windows to get into the hotel and then set fire to trash cans and furniture.

Later on Sunday evening, a far-right mob threw missiles, smashed windows, set fires and clashed with police outside another Holiday Inn housing asylum seekers in Tamworth, Staffordshire.

Meanwhile, further violent riots broke out in Middlesbrough, causing damage to the Crown Court and the university, Cleveland police said.

A group of rioters in Middlesbrough smashed the windows of houses and cars and threw objects at police on Sunday afternoon. One shouted a racist slur and another told police: “It’s our f***ing country.”

Immediately after Sir Keir made his statement, the Home Office announced that additional support would be offered to protect mosques and other potential trouble spots across the country as the crisis gripping the country appears to be deepening.

As police surrounded the mob outside the hotel, the Prime Minister declared that they were “not protesters” and made it clear that their racist behavior “would not be tolerated.”

“There is no doubt that those involved in this violence will face the full force of the law,” he continued. “Police will make arrests. Individuals will be remanded in custody, charges will be brought against them and convictions will follow.”

“I guarantee you will regret participating in these riots, whether directly or through those who instigated this action online and then ran away themselves. This is not a protest, it is organized, violent violence and there is no place for it on our streets or on the internet.”

Violence has rocked cities across the UK after misinformation was used to stoke tensions following the murder of three girls and the attempted murder of seven others in Southport.

Incited by false claims that the suspected attacker was on a watchlist and was Muslim, a far-right mob descended on the grieving Merseyside seaside town last week and laid siege to a local mosque before setting fire to a police car and throwing stones at officers.

Local MP Sarah Champion commented on the gruesome scenes in Rotherham: “I am extremely concerned about the escalating violence at the Holiday Inn Manvers. The people causing damage and attacking police do not represent our city and I am disgusted by their actions. This is criminal disorder and intimidation – not protest.”

Home Secretary Yvette Cooper also seemed to give the police the green light to take tough measures.

“The criminal, violent attack on a hotel in Rotherham housing asylum seekers is absolutely appalling,” she said. “Deliberately setting fire to a building where people were known to be staying. South Yorkshire Police has the full support of the Government in taking strong action against those responsible.”

Tensions were already high in Rotherham earlier in the day when protesters gathered outside the hotel and were greeted by anti-racism demonstrators shouting “refugees welcome”. The situation escalated out of control when anti-immigration protesters threw projectiles at the hotel and attacked police with pieces of wood and chairs. One police officer was dragged away from the scene, believed to be injured.

In his statement, Sir Keir insisted that the scenes were not “protests” but “organised violence”.

“I’m not afraid to call things what they are,” he said. “And that has no place on our streets or on the internet. Right now, there are attacks on a hotel in Rotherham. Marauding gangs are out to break the law. Or worse. Windows are being smashed. Fires are burning. Residents and staff are in absolute fear. There is no justification – none – for this action.”

In a message to those on the right who seemed to offer some justification for the incidents – including Lord Davies, who on Sunday suggested the cancellation of the Rwanda programme was the cause, Donna Jones, the Conservative Party’s Hampshire police and crime commissioner, who suggested in a statement that arrests might not work, and Nigel Farage, leader of the Reform Party UK – he added: “All right-thinking people should condemn this kind of violence.”

“The people of this country have a right to be safe,” he continued. “And yet we see Muslim communities being targeted. There are attacks on mosques. Other minorities being marginalized. Nazi salutes in the streets. Attacks on the police. Indiscriminate violence alongside racist rhetoric.”

The Government has launched a £29.4 million security programme for mosques, which will also benefit Muslim schools. Mosques will be given better protection through new, rapidly deployable emergency security measures, the result of new regulations announced by the Home Secretary today.

The new rapid response procedure means that additional security staff can be made available to mosques at risk of violent unrest, providing vital support and reassurance to communities. This will reinforce the work of local police forces to protect these important places of worship.

Ms Cooper said: “Britain is a proud and tolerant country and no one should excuse the shameful acts of hooligans, thugs and extremist groups who attack police, loot shops or attack people because of the colour of their skin.”