The Retained EU Law (Revocation and Reform) Bill is returning to the Commons today and if passed would make it easier for the government to amend, repeal and replace EU law retained after Brexit.
It also allows nearly all remaining retained EU law to be either repealed or absorbed into UK domestic law by 31 December 2023.
The Wildlife and Countryside Link (WCL) has expressed concern that the bill could see the government changing over 1,000 environmental protections in the UK for the worse.
The report, which was carried out by the Economics for the Environment Consultancy, found that weakening laws in just four of the areas covered by the Bill could cost £82.94bn over 30 years.
These figures come from the damage that could be caused in areas including the health impacts of poorer air and water quality and loss of recycling business opportunities due to weaker chemical regulations.
The WCL said the proposals specifically prohibit new regulations that could impose costs on businesses, even administrative costs, which means that the bill cannot strengthen environmental law, but gives ministers "unprecedented freedom" to weaken it.
Dr Richard Benwell, WCL CEO, said: "Prevention of air and water pollution, protection of precious wildlife and habitats, precautions against hazardous chemical use – they are all put at risk by the Retained EU Law Bill. If long-standing protection for nature is removed or weakened, the economic consequences could run into the billions.
"Add to this the costs of years of uncertainty while half the environmental statute book is up in the air and thousands of hours of civil service time spent reviewing laws simply because of where they came from.
"All together, the costs of this economic and environmental wrecking ball bill could be astronomical at a time when the UK – and our environment – can least afford it."
Some of the major costs include an estimated £20.6bn lost over 30 years from damage to rivers, lakes and coastal waters as a result of losing Water Framework Directive standards.
Losing the standard could see increased levels of agricultural pollutants flowing into UK rivers, along with insufficiently treated wastewater spreading across the water network.
Less air quality improvement could cost £10.4bn over the next five years, rising to £44.9bn over 30 years.
Long-term progress on air quality is at risk due to the weakening of the National Emission Ceilings Regulations, the report warns. Slower progress in improving air quality could see more workdays lost to sickness and increased burdens on the NHS due to conditions including asthma.
Craig Bennett, chief executive of The Wildlife Trusts, said: "Everything about this appalling, anti-democratic and unconstitutional bill is wrong. It is seeking to give ministers the power to remove or amend existing UK legislation on a whim, but this should be the job of Parliament and Parliament alone.
"As things stand, over 1,000 pieces of environmental legislation and regulations will cease to exist at the end of this year, at extraordinary cost to the environment and our economy, and cause untold chaos for business, landowners and farmers in the process."
A government spokesperson said: "The UK is a world leader in environmental protection. Reviewing our retained EU law will not come at the expense of the UK's already high standards and wildlife protections will not be downgraded.
"We have set new legally binding targets under the Environment Act, including to halt and reverse nature's decline. These stretching targets and the Office for Environmental Protection, our new watchdog, means any reform to retained law must deliver positive environmental outcomes."
