60% of animal and plant species studied have declined in the past 50 years.
The State of Nature report, compiled by 25 wildlife organisations - from the RSPB to the British Lichen Society - collates assessments of 3,148 species.
Conservationists hope it will offer clues to the fate of the UK's 59,000 species.
Beetles and wildlfowers are among the most vulnerable species.
According to the document, reasons for the decline are "many and varied" but include rising temperatures and habitat degradation.
Species requiring specific habitats have fared particularly poorly compared to the generalists able to adapt to the country's changing environment.
Turtle doves have declined by 93% since 1970
Hedgehogs have declined by around a third since the millennium
The small tortoiseshell butterfly has declined in abundance by 77% in the last ten years
Natterjack toad numbers have changed little since 1990
The early bumblebee (Bombus pratorum) and the tormentil mining bee (Andrena tarsata) have shown strong declines in range since 1970
The population size of the V-moth is estimated to be less than 1% of what it was in the 1960s
Corn cleavers has undergone one of the most dramatic declines of any plant species
Harbour seals have declined by 31% in Scottish waters since 1996
There is only a single bastard gumwood tree left in the whole world
"This ground-breaking report is a stark warning - but it is also a sign of hope," said naturalist Sir David Attenborough, who launches the report today.
"We have in this country a network of passionate conservation groups supported by millions of people who love wildlife," he said.
"The experts have come together today to highlight the amazing nature we have around us and to ensure that it remains here for generations to come."
Speaking to BBC Radio 4's Today programme, Sir David said there was no single answer to the question of how people could help stem the decline in Britain's wildlife.
Article sourced from BBC