Britain’s biggest environmental groups have warned the government that funding to tackle the climate emergency must be more than double next year to avoid an even greater cost from catastrophic ecological breakdown in the future.

Writing to the chancellor, Sajid Javid, as he prepares to announce on Wednesday his spending priorities for the year ahead, more than a dozen leading environment charities, including Greenpeace and Friends of the Earth as well as other leading organisations such as Oxfam and Christian Aid, said urgent action was required to raise spending.

Spelling out their demands in a costed roadmap for meeting the climate emergency, the groups said that government spending needed to increase from roughly £17bn a year at present to at least £42bn over the next three years. Further increases would be required in the future should the government wish to meet its promise of net zero carbon emissions by 2050.

Failure to deliver the bold rise in expenditure, equivalent to about 2% of economic output each year and around 5% of total state spending, would mean passing on an unsustainable economy with a “planet-sized debt” caused by a climate breakdown, the groups said.

Although broadly welcoming the 2050 target, promised by Theresa May among the final acts of her premiership, the charities said the date needed to be brought forward by several years and that policy and funding arrangements were not yet in place.

In the letter to Javid, the organisations urged the chancellor to demonstrate that he understood the gravity of the challenge by holding a climate and nature emergency budget to unleash a clean industrial revolution in Britain.

Also signed by charities including the Woodland Trust, WWF and Islamic Relief, the letter said higher state investment would encourage more private spending to bring about a low-carbon economy, telling Javid: “Your department holds the key to ending the UK’s contribution to climate change and reversing nature’s retreat, while also setting off a positive economic transformation.”

Boris Johnson had said there would be greater funding for big infrastructure projects but without giving specific details for low-carbon schemes. Polling carried out for the charities by Opinium found a majority of people want ministers to spend more on the climate emergency and nature more broadly.

Among the priorities put forward by the groups are an £11.6bn expansion in transport spending, including a UK-wide car scrappage scheme to remove heavily-polluting vehicles from the roads.

As much as £2.6bn per year should be spent on rewilding projects and other land management schemes, billions should be ploughed into buildings and industry to boost environmental sustainability, while more funding should be given to help communities disrupted by the transition to a low-carbon economy.

John Sauven, an economist and executive director of Greenpeace UK, said: “No one in government is still trying to argue that this is not an emergency, and yet no one in government is acting as though it is.

“We are still constantly pumping carbon into the atmosphere, and trying to ignore the problem will leave our children with a damaged world and a planet-sized debt. There’s a strong economic case and an overwhelming moral imperative for the chancellor to act.”