Police say they may seek to get charges brought against 1,100 Extinction Rebellion supporters they arrested last month as they warned officers would be stretched by a wave of environmental, Brexit and anti-Trump demonstrations this year.

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The Metropolitan police said laws governing protests needed to be reviewed and tougher penalties should be considered for those who broke the law during demonstrations.

Protests by Extinction Rebellion across London over the Easter period led to criticism of the police response and an admission by the Met they should have reacted quicker to avoid disruption across the capital, where Oxford Circus, Westminster Bridge, Marble Arch and Parliament Square were all blocked.

Laurence Taylor, the deputy assistant commissioner, said more than 70 of about 1,100 arrested people had been charged, mainly for minor public order offences.

He said: “All the others are currently under investigation … It is our anticipation that we will be putting all of those to the CPS [Crown Prosecution Service] for decisions.”

A team of 30 officers is carrying out the investigations into the environmental protesters who blocked roads and carried out civil disobedience. Taylor said the officers had been diverted from other duties and would be for months to come. “That’s a really significant resource put in place for a period of six to nine months just investigating that one protest,” he said.

Taylor said the Met supported the right to protest as long as demonstrators obeyed the law. He predicted there would be further action by Extinction Rebellion and from both sides of the hugely divisive Brexit debate. “It is because of those polarised views that it makes it very challenging for the police,” he said.

Taylor said pro-Brexit supporters who had harassed MPs should expect police to intervene, even if it was just to walk alongside the politicians as they went about their business.

Supt Nick Collins, who is involved in policing protests and major events in London, said some of the laws he had to use dated back to the 19th century and that a review of the legislation was needed.

Police are anxious to avoid being criticised for hampering protest in a democracy, but also know they have faced anger for “allowing” disruption to drag on.

Taylor said police and the Home Office had started discussions on the problem. “Protest is not illegal. There is nothing unlawful about protest,” he said.

“The activity of some individuals at a protest can be unlawful. At the moment, there doesn’t seem to be much of a criminal deterrent for doing that and therefore, it doesn’t legitimise it but it does make it easy for that unlawful activity to take place.

“What we would like to see is consequence where the law is clearly broken and it goes beyond what is reasonable and a legitimate aim for a protest, for that to be recognised and for appropriate sanctions.”