Britain's environmental policies on air and water pollution and biodiversity benefit from the country's membership of the European Union, a committee of British lawmakers said in a report on Tuesday.
Based on the findings of an inquiry into the impact of a potential British exit, the Environmental Audit Committee said that EU membership had given Britain a platform to pursue its environmental aims internationally and to influence long-term policy.
It has also ensured that environmental action in Britain has taken place faster and more thoroughly than if it had not been an EU member, the report said.
Even if Britain leaves the EU after the country's referendum on the subject in June, it would still have to follow some EU environmental laws but would be less able to influence how they are developed, the report added.
Ministers told the committee that a vote to leave would result in a "long and tortuous negotiation" with the EU over environmental policy and investors said that Britain quitting the EU - known as Brexit - could remove long-term certainty.
Brexit would also make companies rethink major infrastructure investments in Britain, from waste and recycling to resource management and energy recovery projects, said David Palmer-Jones, chief executive of Recycling and Waste at Suez Environnement.
"The UK has cleaned up its act since we were dubbed the 'dirty man of Europe' in the Seventies," said Mary Creagh, chair of the Environmental Audit Committee.
"EU environmental laws have played a key part and mean we bathe on cleaner beaches, drive more fuel-efficient cars and can hold government to account on air pollution."