A record number of people who have taken part in protests will be in prison in the UK this Christmas, raising concern about the ongoing crackdown on dissent.

Forty people, aged from 22 to 58, will be behind bars on Christmas Day for planning or taking part in a variety of protests relating to the climate crisis or the war in Gaza. Several of them are facing years in prison after courts handed down the most severe sentences on record for direct action protests.

Jodie Beck, a policy and campaigns officer at the civil rights group Liberty, said the number of protesters in prison and the severity of their sentences was “a damning reflection of the state of democracy” in the country.

“We should all be able to stand up for what we believe in without fear of lengthy prison sentences. Continuing to prosecute people for exercising their right to protest will only serve to exacerbate the crisis in our criminal justice system alongside stopping people from making their voices heard,” Beck said.

Nineteen people are in prison – 10 of them on remand – after taking part in climate protests with the campaign group Just Stop Oil. They range from five people who received multi-year sentences after being found guilty of conspiring to cause gridlock on the M25, to two young people jailed for more than 18 months for throwing tomato soup over Van Gogh’s Sunflowers painting in the National Gallery in London.

Cressida Gethin, 22, who is in prison for conspiring to cause gridlock on London’s orbital motorway, told the jury during her trial: “Earth’s life-support systems are breaking down due to human activities … I stand by my actions as the most effective option available to me.”

The other 21 facing Christmas in jail – 19 of them on remand – are alleged to have taken part in pro-Palestinian direct action campaigns, including attempting to disrupt the supply of weapons to Israel from arms factories in Glasgow and Bristol. They include a group who allegedly broke into an Israeli-based defence firm’s site and face charges including grievous bodily harm, criminal damage and aggravated burglary. Their trial is due to take place in November next year.

Since the war in Gaza, many climate justice groups in the UK have swung behind the Palestinian cause and both sets of activists have been at the sharp end of the crackdown on protest, receiving what many experts consider draconian treatment by the legal systems in the UK.

The scale of the incarceration and the length of the sentences has caused widespread concern among civil liberties organisations and legal experts.

Michel Forst, the UN rapporteur on environmental defenders, has described the situation in the UK as “terrifying”, saying protesters are being forced to navigate a draconian new legal environment that includes significant limits on the right to protest.

Earlier this month a report found that the UK is a world leader when it comes to jailing environmental protesters, with police arresting people at nearly three times the global average rate.

A leading barrister, Michael Mansford KC, said that as more people became aware of the “violent global threats to our very existence”, namely the climate crisis and war, “it is hardly surprising that the increasing numbers trapped by these forces are compelled to make their presence and their objections felt as loudly and urgently as possible”.

He added: “If the non-violent exercise of freedom of speech, expression and assembly are to retain a meaningful central role in our democracy, there has to be a paradigm shift in appreciation and understanding of these particular needs by government and the law.”

Over the past few years a raft of new legislation has been introduced that severely curtails the right to protest.

Beck, of Liberty, said: “From votes for women to pride, our society is better for the protests that have come before us. We need a government that listens to, rather than punishes, protesters, and for the dangerous legislation of recent years to be immediately overturned.”

Direct action climate protests are not always popular with the British public. In October, a YouGov poll found that almost three-quarters of people thought the jail sentences given to the National Gallery protesters were either “about right” (37%) or “not harsh enough” (36%).

The policing minister, Diana Johnson, defended the approach to protest, saying that although the government supported people’s right to take to the streets, no one was above the law.

“This government recognises the democratic right that people must be free to peacefully express their views, but they should do so within the bounds of the law,” Johnson said.

Anna Holland, 22, from Newcastle, was one of the two people imprisoned for throwing soup at the Sunflowers painting, and will spend Christmas in Send prison in Surrey. They said life behind bars was “hard” and “scary”, and that being away from their family at Christmas exacerbated those feelings.

However, they said the threat of prison must not silence people in the fight for justice.

“Prison is used as a deterrent, but we must not allow it to deter us,” Holland wrote. “We must not allow fear to win over hope. We must not lose the dream that we can create a better world together.”