England’s EA has told its staff to “shut down” and ignore reports of low-impact pollution events because it does not have enough money to investigate them, according to a leaked internal report.

The ruling on so-called category 3 and 4 incidents means that events such as farm pollution or hazardous dumps by business may not be properly investigated. The decision has infuriated river groups and NGOs.

An Environment Agency briefing to staff, issued in November and seen by the Guardian and the Ends Report, says there is leadership support for “no response to unfunded low- and no-impact environmental incidents”, also known as category 3 and 4 incidents.

The leaked document also hints at the agency’s frustration at ministers and the money set aside for its work. It says the EA’s leadership team has “made it clear to government that you get the environment you pay for”.

Exceptions to the rule will be pollution incidents caused by a regulated site or a water company, says the briefing, although it does not explain how it will determine the source or seriousness of an incident if it is not attended or investigated.

Ignoring the huge number of pollution reports that come in each year will have benefits, says the agency’s briefing, including “reduced overall effort spent on the incidents that present the lowest risk to the environment”, increased effort on “charge-funded regulation”, more space to prioritise higher-risk incidents, “increased consistency of response and service for customers”, and reduced disruption to officers in and out of hours.

In an Environment Agency presentation, also seen by the Guardian, on what is known internally as the incident triage project, the agency states that it currently responds to more than 70,000 incidents each year, and the number continues to increase.

However, data from the agency’s National Incident Recording System shows that while 116,000 potential incidents were reported to the agency in 2021, just 8,000 were attended, and that this number had fallen from 12,000 in 2016, when 74,000 potential incidents were reported.

“We cannot keep trying to do what we are not funded to do; we do not have the money or resources,” states the presentation deck. “We are in an unsustainable position. Our incident responders feel under growing pressure, and this is affecting staff resilience and wellbeing.”

Should staff hear of a category 3 or 4 incident that does not relate to a water company or a regulated site, they are told: “Do not substantiate report, call site or add any details. Shut down report.” Template reply letters have been created for agency staff in anticipation of complaints.

One Environment Agency officer, who did not wish to be named because staff have been warned against speaking to the media, said: “A lot of category 2 incidents start off as 3s until they are attended” and that an example of a category 3 could be a “2km spill of oil or sewage in a river”.

A second officer, who also wished to remain anonymous, said it would be “impossible” to ascertain what level of incident had taken place without visiting it. The EA’s response to pollution had been dwindling for some time, they added, and “unless there were dead fish floating everywhere”, an incident would not be attended by the agency.

The agency’s customer service commitment says the regulator had its budget for responding to environmental incidents cut last year and that as well as slashing responses, it will no longer provide feedback on any action taken to tackle pollution events.

It follows many years of grant-in-aid cuts for the agency. However, the government gave the Department for Environment, Food and Rural Affairs and its agencies an additional £4.3bn in the latest spending review in October 2021. An overview of the Environment Agency’s settlement is due this year.

Mark Lloyd, the chief executive of the Rivers Trust, called the move an “appalling scandal”. He told the Guardian that :“Category 1 and 2 pollution incidents obviously have a very serious impact on the environment, but they are the tip of the iceberg. The vast majority of incidents are in lower categories, and they are what cause the death of rivers by a thousand cuts..

"Resources and political backing to take robust action in all cases of pollution if our rivers are not to continue suffering endemic pollution and an ongoing decline in quality … It is absolutely essential that there should be a credible threat of enforcement for all pollution incidents if we are to restore our rivers to good health for the next generation.”

An Environment Agency spokesperson said: “We focus our incident response effort on those pollution incidents which pose the greatest risk to the environment.

“Our incident triage project is looking at how we can best use our resources and maximise benefits for the environment. While we continue to attend the most serious incidents, we concentrate our efforts on our regulatory activities which prevent incidents from happening in the first place. Intelligence from incident reporting helps us to plan and prioritise our work to protect the environment.”

A Defra spokesperson said: “The government recognises the importance of protecting the nation’s natural environment and we are investing accordingly.

“Defra and its agencies received an additional £4.3bn in the latest spending review in October 2022 so we can do more to tackle climate change and protect our environment for future generations. The Environment Agency plays a hugely significant role in this area and will always seek to hold those responsible for environmental harm to account.”