The US government has not halted a single project out of the 88,000 actions and developments considered potentially harmful to the nation’s endangered species over the past seven years, a new study has found.

An analysis of assessments made by the US Fish and Wildlife Service, published in the Proceedings of the National Academy of Sciences, found that the agency very rarely used its powers to intervene in projects that could imperil any of the US’s endangered plants and animals, which currently number almost 1,600.

Of 88,000 actions assessed by the FWS between January 2008 and April 2015, just two triggered significant further action. A 2007 plan to drop fire retardant in California was deemed by the FWS to be prohibitively harmful to forest-dwelling endangered species, although this was challenged in court. The FWS also stepped in over a plan to divert water from the San Francisco Bay Delta due to concerns over the impact to threatened fish.

In both cases the FWS used a regulation called section seven, which requires a federal agency to consult with the wildlife regulator if it is undertaking, funding or authorizing an action that may be detrimental to an endangered species.

Following an assessment, the FWS can rule that the project would jeopardizes the ongoing survival of the species and require that the project either be halted or altered to lessen the impact. Projects can include developments such as roads and buildings that require a habitat to be flattened or destroyed.

According to Defenders of Wildlife, a wildlife welfare group that conducted the analysis, the FWS is intervening in a diminishing number of cases. A tally from 1991 shows that there were 350 “jeopardy judgements” out of 73,560 previous consultations, compared with the two adverse outcomes in 80,000 cases over the past seven years.

Defenders of Wildlife said that the analysis shows it is misleading to claim that federal wildlife regulations are hampering development and harming jobs.

“The impression we often get from Congress and the media is that the Fish and Wildlife Service makes these calls all the time, that you can’t cut down a tree to build a swimming pool or that you can’t graze cattle on your ranch,” said Ya-Wei Li, the senior director of endangered species conservation at Defenders of Wildlife. “A lot of projects are modified in the first place, but this shows that none of them were stopped or substantially modified in order to avoid the jeopardy finding.”

Li said it was unclear whether planned projects are now more environmentally friendly than in the past, but the study suggests that the FWS was disinclined to halt developments.

“We know that the Fish and Wildlife Service is really understaffed, which makes it harder for them to do the work to make that call,” he said. “It’s hard to believe that federal agencies have got so much better at conservation, there now seems to be a more stringent threshold for damage done before projects are challenged.”

“The Service are culturally less inclined to rock the boat,” he said. “We need to take a step back and consider whether section seven is adequately protecting our species.”

A FWS spokeswoman said the agency had not seen the study but that it was confident the section seven process was working effectively.

Last week, the FWS received plaudits from conservation groups after it issued a draft of new rules that would provide greater scrutiny of oil and gas extraction within the National Wildlife Refuge System.

Currently, FWS only administers the surface of wildlife sanctuaries it purchases. This means that private entities that own the ground beneath the sanctuaries can exploit it for resources. More than 100 wildlife refuges across the US have been turned into oil and gas drilling sites as a result.

The new regulations will allow owners of the subsurface to retain their rights but there will be greater regulation of the activity that takes place within wildlife refuges.