The study found the total abundance of species, including birds, bees, butterflies and trees, has declined on average by almost a fifth in 50 years.

The State of Nature report, thought to be the most comprehensive review of Britain's wildlife ever, blamed the losses on farming, climate change, unsustainable fishing and marine development.

Craig Bennett, CEO of The Wildlife Trusts, one of the organisations involved, said: "Nature recovery is fundamental to tackling climate change and improving people's lives - history will not be kind to politicians that ignore this truth."

Fiona Matthews from Sussex University, a report author, added: "If we don't have biodiversity, we don't have a planet. It's as simple as that.

"We want to pass on the planet that's still functioning to the next generation. And at the moment, simply we're failing to do that."

The State of Nature study, produced by dozens of conservation organisations, found that 16% of more than 10,000 plants and animals assessed could disappear from the UK.

It said familiar species such as the turtle dove, hazel dormouse, and European eel all now "face an uncertain future", while the spread of more than half of flowering plant species like heather and harebell has dropped too.

In all, nearly half of the UK's bird species, almost a third of its types of amphibian, reptile, fungi and lichen and a quarter of its land-living mammals are under threat.

Environment Secretary Therese Coffey said in a statement: "The UK's nature is a crucial part of our islands.

"That is why we put in law the requirement to halt the decline in nature and protect the abundance of species, why we are committed to increasing the amount of habitat for nature to thrive and why we were one of the first countries to pledge to protect 30% of our land for nature by 2030."

However, two separate assessments this year suggested that only around 3-6% of land is currently protected, something regarded as crucial for allowing species to bounce back.

The UK is one of the most nature-depleted countries on Earth, according to a 2021 study, while today's report warned the UK now has less than half of the plant, animal and fungal life it once had remaining, as a result of human activity.

Tanya Steele, chief executive of wildlife group WWF UK, told Sky News: "There's no doubt we have seen successive governments not stepping forward."

She praised the current government for setting "very clear targets" on nature, including an aim to stop the decline by 2030.

But she said it needed to ramp up policies and investment "to actually deliver on that trajectory".

This year the government did overhaul payments to farmers to help them protect nature. It has also created or restored wildlife habitats the size of Dorset, and launched 12 nature recovery areas.

However, the government has also come under fire this year for failing to tackle sewage and farm pollution in waterways, attempting to relax some rules on water pollution, a move later thwarted in the House of Lords, and for rowing back on some key measures to tackle climate change.

Ms Coffey added: "We also continue to clean up our rivers, plant more trees and through our world-leading environmental farming schemes support farmers to produce food sustainably and profitably."

The report did offer some good news, however, with animals like bitterns, cranes, red kites and the large blue butterfly making a comeback thanks to conservation projects.

But the overarching figures show little improvement from the last edition of the report, published in 2019.

It was the year Boris Johnson swooped to victory in the general election, partly on a ticket to restore nature.

He, as well as former prime minister Theresa May and current premier Rishi Sunak, have all pledged to leave the environment in a better condition than they found it in.

But "despite progress in ecosystem restoration, conserving species, and moving towards nature-friendly land and sea use, the UK's nature and wider environment continues, overall, to decline and degrade," the report said.

Watch The Climate Show with Tom Heap on Saturday and Sunday at 3pm and 7.30pm on Sky News, on the Sky News website and app, and on YouTube and Twitter.

The show investigates how global warming is changing our landscape and highlights solutions to the crisis.