Actor Emma Watson and singer Ellie Goulding joined about 450 female politicians, academics and activists on Thursday to demand equal representation for women on Britain’s male dominated team hosting next year’s U.N. climate summit.

In a letter to British Prime Minister Boris Johnson, they warned that the lack of women in COP26 leadership positions would undermine the summit’s credibility and success.

There was outcry in September when British media reported that the government had appointed an all-male team to host COP26. Johnson has since appointed former aid minister Anne-Marie Treveylan to one of the top four positions.

“It is incomprehensible that half the planet is not represented in the senior leadership team … when it is widely acknowledged that the role of women is critical in tackling the climate and ecological emergency,” the letter said.

Signatories include actor Emma Thompson, former Irish president Mary Robinson, model Lily Cole, Nobel Prize winner Jody Williams, philanthropist Chelsea Clinton and Laurence Tubiana, an architect of the Paris Agreement on climate change.

Heads of state, climate experts and campaigners from across the globe are due to gather in Glasgow next November after the talks were delayed by a year because of the COVID-19 pandemic.

The COP26 talks are seen as a make-or-break moment for the 2015 Paris Agreement as governments are due to submit climate action plans to limit warming to “well below” 2 degrees Celsius above pre-industrial times.

A government spokesperson said Britain was “committed to championing diversity” and 45% of senior management in the COP26 unit were women, but activists said most were in more minor supporting roles.

The COP26 website appeared to show only two women among the top 10 named appointments.

The letter said women and girls bore the brunt of climate-related disasters and were generally more supportive of policies and lifestyle changes to tackle the issue.

“They are the ‘shock absorbers’ of climate change,” signatories said.

“Impacts disproportionately hit their livelihoods and food security, drive up levels of the violence they experience, and hold them back from engaging in education and the green economy.”

Signatory Malini Mehra, chief executive of parliamentary network GLOBE International and an Indian climate campaigner, said the government was sending the wrong signal.

“The COP26 presidency is a test of the UK’s commitment to gender equality. Women are half the population and must be half the top table,” she said.