Britain’s most senior police officer has defended the arrest of six anti-monarchy protesters and hit out at “ill-informed commentary” amid fierce criticism of the action taken.

Writing for the Evening Standard, Metropolitan Police chief Sir Mark Rowley said it was “unfortunate” that the demonstrators were unable to join fellow activists on Saturday following their detention.

The six were the first arrests to be made under the sweeping Public Order Act, under suspicion of going equipped to “lock-on” – a measure protesters use to make it harder for police to move them.

Prime Minister Rishi Sunak defended the new powers, which came into force last week, saying it was right for officers to have the power to tackle “serious disruption”.

Sir Mark wrote in the Standard: “While it is unfortunate that the six people affected by this were unable to join the hundreds of peaceful protesters, I support the officers’ actions in this unique fast-moving operational context.”

The six campaigners from Republic were arrested early on Saturday morning and detained for 16 hours.

They were released without charge after police conceded it could not be proved whether the protesters intended to lock-on.

Republic’s chief executive Graham Smith, who was among those arrested, is considering legal action against the Met after officers personally apologised to him over what he called a “disgraceful episode”.

He said three “rather embarrassed” officers apologised to him at his home in Reading, Berkshire, before handing back the straps for the placards they arrested him over.

“I said for the record I won’t accept the apology. We have a lot of questions to answer and we will be taking action,” he told the PA news agency.

Mr Sunak told broadcasters during a visit to Southampton: “Of course people have the right to protest freely but peacefully, but it is also right that people have the ability to go about their day-to-day lives without facing serious disruption.

“What the Government has done is give the police the powers that they need to tackle instances of serious disruption to people’s lives.

“I think that is the right thing to do and the police will make decisions on when they use those powers.”

The police and the Home Office have to get straight exactly how they protect our democratic rights at the same time as protecting the day for thousands of people

In total, 64 people were arrested over the weekend, of which 52 were over police concerns that the coronation may be disrupted.

Sir Mark said it was “frustrating” the force could not share more information about some of the arrests while investigations continue.

He said: “I can report that we found people in possession of possible lock-on devices and people that appeared to be purporting to be stewards of the event in possession of plastic bottles containing white paint, which we believe were specifically to be used to criminally disrupt the procession and resulted in arrests for going equipped to commit criminal damage.

“Much of the ill-informed commentary on the day is wholly inaccurate – for example, protest was not banned.

“I want to be absolutely clear – our activity was targeted at those we believed were intent on causing serious disruption and criminality.”

Mayor of London Sadiq Khan has asked for further information about why the Republic supporters were arrested, as well as volunteers for Westminster City Council charity Night Star which hands out rape alarms.

The leader of the council has requested an apology from the Met after all three Night Star volunteers were released without charge.

Cllr Aicha Less, deputy leader and cabinet member for Communities and Public Protection, said: “We have met with the Metropolitan Police to discuss the arrest of our Night Stars, about which we have been deeply concerned.

“We are pleased to confirm that all three of our volunteers, who provide such a valuable service to the community, have been released without charge and will not face any further action.

“In addition, the Leader of the Council, Cllr Adam Hug, has also written to the Commissioner of the Metropolitan Police today, setting out the reasons for our concerns about the handling of this matter. He has also requested an apology is made to the three volunteers.

“We continue to offer our Night Stars our full support and are also mindful about the potential impact of this matter on our night safety work, much of which is reliant upon members of the public giving up their free time. That’s why we will continue to work with the Metropolitan Police to keep the city safe and to learn from this unfortunate incident.”

Former Greater Manchester Police chief Sir Peter Fahy said the Public Order Act used to detain the protesters was “very poorly defined and far too broad”.

Senior Tory MP David Davis called the legislation “too crude” and urged the Commons Home Affairs Committee to investigate.

Sir Peter told BBC Radio 4’s Today programme: “We see the consequences of that particularly for the poor police officers who have got to try and make sense of the legislation that was passed only a few days ago.

“This could affect all sorts of different protests in your local community, when you’re unhappy about HS2 or a housing development or whatever, this legislation could be used against you, and the police would be under pressure.”

Mr Davis, a former Brexit secretary, said the arrests show the legislation is “too crude, too poorly defined”.

“The police and the Home Office have to get straight exactly how they protect our democratic rights at the same time as protecting the day for thousands of people,” he told Today.

“The whole law is defined really very broadly. It’s also true for the stop-and-search powers as well. There are a whole series of elements of law which are just too broadly defined.”

Downing Street was clear that it thinks the new powers are “appropriate” and “in line with what the public want”.

“It wouldn’t be right to judge a whole piece of legislation based on one example,” the Prime Minister’s official spokesman said.

He said that the Home Office had “business as usual” conversations with the Met ahead of the policing operation, after Republic demanded to know whether officers were acting at the behest of politicians.

Home Secretary Suella Braverman attended a number of meetings with the Metropolitan Police ahead of the coronation, the PA news agency has been told.

A Whitehall source characterised them as routine updates on the force’s expectations and preparations for the operation, stressing the police remain operationally independent.