Police are increasingly using "heavy handed" tactics against protesters, a committee of MPs has warned ahead of the G20 summit being hosted in London.
The Joint Committee on Human Rights said it was concerned the right to protest was being undermined by "autocratic" police measures.
Anti-terror powers were being "misused" to restrict lawful protest, the committee said.
The report found no "systematic" human rights abuses but urged changes in the law and police methods.
MPs called for police to be instructed on human rights as part of their general training.
But they said protesters had a responsibility to engage with police officers during the planning of their protest to help avoid violence.
Committee chairman Andrew Dismore said: "The right to protest is a fundamental democratic right and one that the state and police have a duty to protect and facilitate.
"Of course there is a balance to be struck between the rights of protesters, the police and the public, but the state must not impose restrictions unless it is necessary, and proportionate, to do so.
"That is a high threshold. The presumption is in favour of protest without state interference. We believe there are changes to the law and practice that are needed to make that presumption a reality."
Protesters claimed officers policing last year's Climate Camp in Kent confiscated tent pegs and a clown costume. At one point 1,500 officers, including riot police, were dealing with only 1,000 protesters, organisers said. Kent Police have asked the police watchdog to investigate how they policed the event.
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