The next government must bring forward the target for reaching net-zero carbon emissions by five years to 2045, phase out diesel and petrol cars by 2030 instead of 2040, and start devoting at least 5% of all government spending to the climate and the restoration of the UK’s natural environment, a broad coalition of civil society groups has demanded.

They have written to the leaders of all the UK’s main political parties, citing the UK’s hosting of next year’s UN conference on the climate, known as COP26, as the catalyst for strengthening existing goals in line with scientific advice.

“[Next year] will be crucial for the future of our planet and presents opportunities for the UK to enhance its reputation as a global leader on these issues,” they wrote, on 17 October, before the general election was called. “Global leadership will depend on strong evidence of domestic delivery.”

Alongside green groups such as Greenpeace, WWF and Friends of the Earth, the signatories include the Women’s Institute, the UK Health Alliance on Climate Change, development charities including Oxfam and Tearfund, and religious organisations such as Islamic Relief, Quakers, GreenChristian and Cafod, the Catholic Agency for Overseas Development.

Another letter calling for a more ambitious environment act, reform to the farming sector that prioritises environmental protections, tougher commitments to end overfishing, and a closer relationship with the EU on green issues, was sent by organisations with 8 million members, including the National Trust, RSPB, the Campaign to Protect Rural England, the Woodland Trust and Greener UK.

Separately, the UK’s largest business organisation, the CBI, called on the next government to “kick off a decade of climate change action”, demanding tougher regulations to make buildings more energy efficient, clear policies to drive the uptake of electric vehicles, a new post-Brexit carbon pricing regime for businesses, and a new strategy for carbon capture and storage.

“We are asking the government to turn 2020 into a year of action,” said Carolyn Fairbairn, director general of the CBI. “We have the deadline of the COP26 climate conference in Glasgow next November, so let’s use it to kickstart the UK’s net-zero plans and see how much we can achieve in the next 12 months.”

Referring to the success of the London Olympics in 2012, which had a galvanising effect on the UK’s international sporting performance, she added: “[COP26] could be our climate change Olympics, reinforcing the UK’s position as a global climate leader, as well as showing the public at home, and the wider world, the scale and reach of UK low-carbon innovation and expertise.”

All of the major parties are expected to set out commitments on the climate emergency and the environment as a key part of their election planning. The Conservatives made a U-turn on fracking at the weekend by pledging a moratorium that will in effect end fracking in the UK for the near future, though critics said it fell short of a permanent ban.

John Sauven, executive director at Greenpeace UK, said environmental issues must play a leading role in every party’s strategy: “As carbon emissions, global temperatures and sea levels continue to rise, public concern over the climate and nature emergency is also rising. Election manifestos must reflect this by providing clear and ambitious policies that will take us to a net-zero carbon world and restore nature as quickly as possible. This isn’t about winning over voters with warm words; it’s about committing to a tangible roadmap that will help save the planet from climate and ecological collapse.”

Doctors are also increasingly concerned about the impacts of climate chaos, according to Richard Smith, chair of the UK Health Alliance on Climate Change, which represents more than 650,000 health professionals. “As the chief executive of NHS England has said, the climate emergency is a health emergency,” he said. “[And] air pollution is responsible for around 40,000 premature deaths each year, so the UK’s commitment to banning new petrol and diesel cars should be brought forward to 2030 to reduce pollution and save lives.”

The climate emergency is also being taken up by organisations beyond dedicated green and conservation charities, including faith groups and charities with a community and volunteering focus.

Lynne Stubbings, chair of the National Federation of Women’s Institutes (NFWI), said her members were taking action locally, by planting trees and creating community gardens among other efforts, and wanted to see more action from the government.

“WI members are clear that we need urgent action to tackle climate change, stop our oceans and wildlife being destroyed by plastic pollution, and to protect our environment for the future,” she said. “The WI has been at the forefront of efforts to protect our environment since the 1920s with campaigns ranging from raising awareness of ocean pollution, to the scourge of litter and the need to tackle wasteful excess packaging.”

The Green party welcomed the calls for greater emphasis on the climate and other environmental issues, and said faster action was needed. “Business has a crucial part to play in the urgent transformation we need to see and government should unleash its potential,” said its co-leader Jonathan Bartley. “The next decade will be vital to take the necessary steps to halt climate chaos. It is only through an alliance of state and non-state actors that we will be able to make the UK a world leader in the green revolution we need to see.”