The public wants a televised leaders' debate on the climate and nature emergencies.
More than 120,000 people have signed a petition calling for a televised election debate among party leaders on climate change and nature.
But organisers of the campaign say they have been told that Prime Minister Boris Johnson will not take part over fears the issue could be "siloed", though other party leaders have agreed to the debate.
The call has been led by climate charity Possible and the UK Student Climate Network, amid growing concern over climate and environmental crises.
It comes as parties vie for votes with announcements on green policies, and as parts of England have been hit by torrential rain and flooding, which experts warn will become more likely with climate change.
More than half of those quizzed in a recent poll for environmental lawyers ClientEarth, before the General Election was called, said climate change would influence how they voted, and 63 percent said they did not feel politicians were talking about it enough in the run-up to the election.
The move for a climate debate has been backed by more than 60 organisations totalling millions of members, including the Women's Institute, the National Union of Students and the National Trust.
Max Wakefield, director at Possible, said: "It's clear from the level of diverse support we've received in just a week that the public wants a televised leaders' debate on the climate and nature emergencies.
"Given that, why wouldn't the government want to make the case for their market, innovation and regulatory-based approach to tackling these emergencies?"
Cate Davies, campaigner for the UK Student Climate Network, said a dedicated debate on "the greatest issue of our time" would not isolate it.
"It would finally, after it being essentially absent in previous electoral cycles, give it the attention it deserves and shine a light on just how closely the climate and nature emergencies impact other issues such as housing, health and security."
Greenpeace UK is supporting the demand for a TV debate, and the campaign group's Rebecca Newsom said: "Brexit or no Brexit, the environmental crises that we currently face are the most pressing issues of our time.
"Voters are aware of this and it's clearly going to influence how they cast their ballot.
"This is why all party leaders must showcase their policies for tackling the climate and nature emergencies to the public, and allow them to be scrutinised, by taking part in a climate and environment TV debate." The Conservative Party has been approached for comment.
Emily Beament is the PA environment correspondent.