Much of the UK's natural environment is "still deteriorating", with costs to the economy and businesses, an official report has found.
The Government has pledged to be the first generation to leave the environment in a better state than it found it, and is set to produce a 25-year plan setting out how it will deliver on the promise.
Its N atural Capital Committee, which looks at parts of the environment that provide valuable goods and services such as flood protection and good soils for growing food and storing carbon emissions, said the Government's pledge was "achievable".
But currently, natural assets and the benefits they provide are in decline, with costs becoming "increasingly apparent" in flooding, soil degradation, air pollution, declines in pollinating insects and loss of outdoor recreation areas, it said.
Reversing the declines is needed to reduce costs and secure the benefits of a good quality environment such as better health, educational opportunities, tourism, carbon storage, flood protection and more wildlife, a report by the committee said.
The committee called for the 25-year environment plan to be moved forward rapidly to deliver improvements in natural resources before 2020, blaming slower-than-expected progress on the plan in part on the referendum and Brexit.
The plan should be put into legislation to ensure it is implemented, and should contain "ambitious, long-term" outcomes for natural assets, a new report from the committee recommended.
There also needs to be a programme of investment in natural resources, such as land and water, by the private and public sectors, it said.
England's National Parks, which contain some of the country's most important natural areas, should see their powers and duties extended to support the 25-year environment plan, it added.
The committee also called for plans for the environment to be closely integrated with British agricultural policy from 2020, after the UK leaves the EU-wide subsidies scheme as part of Brexit, as farming dominates activities on 70% of UK land.
The report said: " Currently many aspects of the natural environment are still deteriorating.
"Although there are examples, such as these, where specific action has successfully been taken to protect and improve natural capital, the overall picture is one of continuing decline: both in terms of individual assets and the benefits they provide."
There are also challenges in delivering on the 25-year environment plan in the face of a growing population, a major housebuilding programme and significant infrastructure development, it said.
Responding to the report, the chairwoman of the parliamentary Environmental Audit Committee, Mary Creagh, said: "It is time for the Government to place the environment at the heart of its decision-making.
"The Environmental Audit Committee has called for a new Environmental Protection Act to address the gaps that will be left by leaving the European Union.
"It is good to see the Natural Capital Committee endorse our view that new legislation is needed to oversee and enforce Defra's 25-year plan for the environment and to reverse the trends that have eroded our natural environment."
An Environment Department (Defra) spokeswoman said: "Our ambition is to be the first generation to leave the environment in a better state than we found it, and we are committed to building on our long history of wildlife and environmental protection.
"As we leave the EU, we have a unique opportunity to develop tailored environmental policies for our country and we will consider the recommendations outlined in this report."