Camped outside the main entrance of New Broadcasting House on Friday morning, Extinction Rebellion (XR) supporters called on the broadcaster to “tell the full truth” about the climate crisis, as the number of arrests linked to its protests since Monday rose to more than 1,100.

Protesters held a banner stating: “BBC, your silence is deadly”, and chanted: “Whose BBC? Our BBC”, and: “BBC, can’t you see, this is an emergency”.

It came as the Metropolitan police continued to arrest activists at Trafalgar Square, XR’s last remaining protest site in Westminster, after the police commissioner, Cressida Dick, used an Evening Standard article to criticise protesters, saying that their strategy pulled her officers “away from priorities”.

“We are not anti-protest – but we are against them repeatedly breaking the law,” she wrote.

Across the Thames, hundreds of activists had decamped to the Vauxhall Pleasure Gardens, where they were constructing a new protest camp in preparation for another week of action in the capital.

Q&A What are Extinction Rebellion's key demands? Show The UK group of Extinction Rebellion has three core demands: 1) Tell the truth

The government must tell the truth about the scale of the ecological crisis by declaring a climate emergency, “working with other groups and institutions to communicate the urgent need for change”. 2) Net zero emissions by 2025

The UK must drastically cut its greenhouse gas emissions, hitting net zero by 2025. 3) Citizens’ assembly

The government must create a citizens’ assembly to hear evidence and devise policy to tackle the climate crisis. Citizens’ assemblies bring together ordinary people to investigate, discuss and make recommendations on how to respond, in this case, to the ecological emergency. In the US activists have added a further demand: “A just transition that prioritises the most vulnerable and indigenous sovereignty [and] establishes reparations and remediation led by and for black people, indigenous people, people of colour and poor communities for years of environmental injustice.” Matthew Taylor

The latest round of XR protests began on Monday under grey skies. As commuters hurried past, a black hearse parked across a busy junction at the foot of Nelson’s Column. Inside, the driver locked his head to the steering wheel using a bicycle lock, as others scrambled to lock themselves to the underside of the vehicle.

It was one of 11 sites taken at the beginning of the week by decentralised XR groups that had travelled to London from towns and cities across the UK. Every night this week representatives from each site met in private to discuss what has gone well that day, and to work out what comes next.

During the April protests 1,100 people were arrested over two weeks, in what was described as the largest act of civil disobedience in a generation. By Friday morning – four days into the latest action – that arrest record had already been reached.

But there have been fresh challenges for those taking part this week.

Shortly after the hearse was in place on Monday morning, Larch Maxey had his hands on scaffolding being brought into Trafalgar Square when he said an officer grabbed him, snapping his finger “like a carrot”.

“The police just pounced on me and one of them just decided to grasp my index finger really forcefully and snap it,” he said.

The XR hearse blocks an entrance to Trafalgar Square. Photograph: Guy Bell/Rex/Shutterstock

It was just one of numerous allegations that have emerged against the police this week.On Friday the legal environment charity Plan B wrote to the Met commissioner citing what it said were “numerous instances of human rights violations” by the police.

The allegations included “armed police, carrying rifles, stopping members of XR and ordering them to put their hands in the air; a plain clothes police officer attempting to incite violence in the crowd; arbitrary and aggressive use of stop and search powers; and officers forcefully removing tents without checking whether children or others were inside”.

In response, the Met said it had received the letter and was “considering its contents”.

Those involved with this week’s protests say more forceful policing has combined with a different political climate – and harsher weather – to create an edgier, harsher mood on the streets than in April. Then the sun came out, and there was a feeling of relief among some of those taking part that they were finally voicing the truth about the scale of the climate crisis.

This time, says Ronan McNern, from XR’s media team, “they have definitely made it more difficult and less open to vulnerable people, or people who are just not used to this sort of thing, to get involved”.

While the protests have forced the climate crisis up the agenda, with XR representatives on TV and radio throughout the week, the police action has dominated the news and some organisers fear that, alongside a focus on “hippy dancing” – as one put it – the coverage had obscured the diverse voices of those taking part, from grandparents to young people, scientists to young mothers.

Ursula Pethik, 83, from Hastings, joined the XR protests on Whitehall on Wednesday with her friend John Lynes, 91. She dismissed the idea the demonstrators were all “uncooperative crusties” , as Boris Johnson put it.

“This was not fun for me,” she told the Guardian. “This was no party, there was no cocaine or dancing or whatever they are trying to say!

“I am old and it was very painful and difficult. This is not something we are doing lightly but we realise we have no other choice.”

After she glued herself to the road, both her and her 91-year-old companion were arrested, with Pethik being released from Wandsworth police station at 2am after 10 hours in a cell.

“My generation is largely responsible for the situation that young people today face and I just need to do something … not just for my grandchildren but for children and future generations everywhere.”

For XR, the calculation is whether they can get enough people arrested to overwhelm the system so that police chiefs go back to politicians and say they need to engage with the protesters’ three demands: to tell the truth; to reach net zero carbon emissions by 2025; and to set up a citizens’ assembly.

But no one knows whether that means 2,000 arrestees or 5,000. On Friday the Met said it was “a large organisation with thorough contingency plans regarding cell capacity”.

The mood in the new protest camp in Vauxhall was upbeat. Tents, gazebos and banners were set up in the muddy drizzle, as kitchens handed out food and hot drinks. Local businesses have made donations and offered the use of toilets, said activists, who are now planning a series of “big disruptive actions” for next week.

Ben Kenward, an XR activist and psychology lecturer at Oxford Brookes, said: “We are learning a lot. In a sense this is XR’s difficult second album. Do we do the same thing again? Will it work? We are experimenting.

“We’ve learned a lot about police tactics. Now they’ve changed their tactics, so we are going to learn from that and respond.”