The legitimacy of the Cop26 climate summit has been called into question by civil society participants who say restrictions on access to negotiations are unprecedented and unjust.

As the Glasgow summit enters its second week, observers representing hundreds of environmental, academic, climate justice, indigenous and women’s rights organisations warn that excluding them from negotiating areas and speaking to negotiators could have dire consequences for millions of people.

Observers act as informal watchdogs of the summit – the eyes and ears of the public during negotiations to ensure proceedings are transparent and reflect the concerns of communities and groups most likely to be affected by decisions.

But their ability to observe, interact and intervene in negotiations on carbon markets, loss and damage and climate financing has been obstructed during the first week, the Guardian has been told.

“Civil society voices are critical to the outcome of Cop, but we’ve not been able to do our jobs. If participation and inclusion are the measure of legitimacy, then we’re on very shaky grounds,” said Tasneem Essop, the executive director of Climate Action Network (CAN), which represents more than 1,500 organisations in over 130 countries.

CAN is one of two environmental “constituencies” – loose networks of NGOs including youth groups, trade unions, indigenous peoples, business, agriculture, and gender – recognised by the UNFCCC.

Gina Cortes, a member of the Women and Gender Constituency, representing women’s groups, said they also had to “call out the deep inequities and deep injustices of this Cop”.

“There are thousands of activists who should be here but who are missing and there is a shocking degree of closing space for civil society and frontline voices … it is offensive, unjust and unacceptable,” said Cortes.

In the run-up to Cop26, the UK government had boasted that Glasgow would be the most inclusive summit on record.

In reality, about two-thirds of civil society organisations who usually send delegates to Cop have not travelled to Glasgow due to “vaccine apartheid”, changing travel rules, extortionate travel costs and Britain’s hostile immigration system.

Observers say the situation was most critical during the two-day leaders’ summit at the start of last week, when they were limited to one or two tickets per constituency despite six negotiating rooms operating simultaneously. In addition, work stations, offices and restaurants were also cordoned off, preventing observers from having face-to-face contact with negotiators.

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“The level of restrictions was unprecedented,” said Sebastian Duyck, from the Centre for International Environmental Law. “It’s alarming, because the relationships we build at the start of Cop are crucial to the work we do after … the limited participation absolutely undermines the credibility of Cop.”

Access has improved since the ticketing system was lifted, with one observer per constituency now technically allowed in each meeting room – if there’s enough spaceaccording to social distancing rules. But their ability to participate meaningfully remains limited.

Observers are particularly concerned about negotiations over carbon trading protocols, as governments and corporations look for ways to achieve net zero commitments using offsets.

“There’s a real risk that decisions made in these rooms will impact human rights in the most dramatic fashion, like we saw happen under the carbon trading mechanism under Kyoto. If we get a bad rule, it’s almost impossible to fix afterwards. The scale of carbon markets means there’s a greater threat to communities,” said Duyck.

This is a huge worry for indigenous communities, who comprise 6% of the global population but protect 80% of the planet’s biodiversity. “Without our voices this risks the creation of rules that will continue to violate human, territorial and spiritual rights of Indigenous Peoples,” said Eriel Deranger, an observer for Indigenous Climate Action.

The UK government points to the unprecedented challenges posed by the pandemic, and says access has been boosted by the new online platform that has so far been used by 12,000 people.

But for some, trying to follow what’s going on virtually, technical glitches have made access a “logistical nightmare”, said Hellen Kaneni, regional Africa coordinator for the international nonprofit Corporate Accountability. “Cop has never been credible but this year it’s much worse, access has been limited in so many ways, it’s horrible.”

Aderonke Ige from Corporate Accountability and Public Participation Africa, who made it to Glasgow from Nigeria for her first Cop despite the Covid restrictions, said she felt “disappointed and unfulfilled” after failing to get online and being denied access to the meeting rooms and offices of the African group negotiators.

A spokesperson said: “The UK is committed to hosting an inclusive Cop. Ensuring that the voices of those most affected by climate change are heard is a priority for the Cop26 presidency, and if we are to deliver for our planet, we need all countries and civil society to continue demonstrating their ideas and ambition in Glasgow.”

The success of this Cop will be judged over years to come. But according to Nathan Thanki from Demand Climate Justice (the second environmental constituency), the summit’s legitimacy had been seriously undermined by restrictions in access and the way rich countries had used Cop26 to make headline-grabbing announcements outside the UNFCCC’s pledge and review framework.

“It’s impossible to monitor these announcements, which means there’s no accountability to civil society or other countries. That’s the sorry situation at this summit.”