Sir Keir Starmer has said swift justice, including sentencing, has been a deterrent to more violent disorder.
At least a dozen people were jailed on Thursday for their part in the riots of the past 10 days, with more expected to be sent to prison on Friday, including some on live television.
The Prime Minister addressed his third emergency Cobra meeting since the first riot in Southport on July 30 and after many planned protests failed to materialise on Wednesday night.
Sir Keir told the meeting that police need to remain on “high alert”, the PA news agency understands.
He is understood to have said there was no doubt that levels of policing in the right places and swift justice over the past week, including sentencing, have acted as a deterrent to disorder.
Earlier in the day he told reporters that Wednesday night’s events turned out “much better than was expected” and “anybody involving themselves in disorder, whatever they claim as their motive, will feel the full force of the law”.
“It’s important I repeat that because we need to make sure that in the coming days we can give the necessary reassurance to our communities, many of whom – I’ve been talking to some this morning – are very anxious about the situation.”
His comments came as the final child injured in the Southport stabbings which sparked the riots was discharged from hospital on Thursday and will continue her recovery at home, Merseyside Police said.
Her family said they were “deeply saddened by the recent disorder”, including attacks on police, and praised the officers who were first on the scene “when the horrific events unfolded” on July 29.
It has been an “incredibly difficult time for our nation”, they said.
More of those arrested in the violent disorder of the past week will appear in court on Friday and about 150 charges have been brought over the unrest.
Defendants will be sentenced at Leeds Crown Court for racially aggravated harassment and publishing written material intended to stir up religious hatred.
Cases will also be heard at Crown Courts around the country, including Newcastle, Teesside, Liverpool, Sheffield and Inner London.
The arrest figure is expected to “continue to rise significantly”, the National Police Chiefs’ Council (NPCC) said.
By Thursday afternoon the total number of arrests stood at 483, it added.
Many planned events failed to materialise on Wednesday but Gavin Stephens, chairman of the NPCC, warned those “intent on violence and destruction have not gone away”.
About 110 protesters gathered in Barnsley town centre, while stop and search powers were put in place in Southport from 2pm on Thursday to 4am on Friday after last week’s violence.
Mr Stephens suggested police patrols could be stepped up at lower league matches at the start of the football season this weekend amid concerns there could be flare-ups at forthcoming fixtures.
“We’ve seen on the footage that we get back from the scene, young people, children, are on the fringes of it, and in that mob mentality can get drawn in,” he told reporters.
“I think the youngest arrest was 11 years old. So, I think to have conversations with young people, children, teenagers over the course of the next few days is really, really important.”
Home Office minister Dame Diana Johnson said social media giants have an “obligation” to deal with criminal offences being committed on their platforms.
She said: “If there are criminal offences being committed on social media platforms now, then these social media companies have an obligation now to deal with that.
“If they’re having incitement to violence on their platforms, that needs to be dealt with now, today. We don’t need the Online Safety Act to deal with that.”
Cumbria Police said a man was jailed within 24 hours of posting racially aggravated, offensive online content on social media.
Billy Thompson, 31, of Mill Street, Maryport, admitted an offence under section 127 of the Communications Act and was sentenced to 12 weeks in prison.
The court heard how, on Wednesday, he posted a racially aggravated and threatening comment on a Facebook social media post informing the public of a dispersal order being imposed in Carlisle relating to potential planned disorder, police said.
He was arrested the same day, charged on Thursday and appeared before North Cumbria Magistrates’ Court and was in jail by the evening.
Richard David Williams, 34, of Maes Deri, Ewloe, Flintshire, was charged with malicious communications and will appear in court on Friday, North Wales Police said.
Arrests continued throughout Thursday.
A 55-year-old woman from Chester was arrested and is being held in custody in relation to a social media post which contained inaccurate information about the identity of the suspect in the Southport murders.
A 38-year-old man from the Weymouth area was arrested on suspicion of violent disorder and assaulting an emergency worker in connection with protests that took place in the seaside town on Sunday, Dorset Police said.
The Metropolitan Police arrested a man in his 50s in south-east London on suspicion of encouraging murder after a video emerged of a Labour councillor calling for far-right protesters’ throats to be “cut”.
He had also been arrested for an offence under the Public Order Act following the incident in Kent.
A Labour spokesperson confirmed that Ricky Jones, a borough councillor in Dartford, Kent, has been suspended by the party in relation to the video.