By SPENCER ACKERMAN

A new Senate bill authorizing the next year’s worth of intelligence operations would force the public disclosure of civilian deaths in drone strikes and add protections for spy-sector whistleblowers that are being hailed by advocates.

The bill, which was approved in the Senate intelligence committee this week by 13 votes to two, would require the president to provide greater visibility than ever before into the controversial drones programme.

Each year, the president would have to “make public” a report listing “the total number of combatants killed or injured during the preceding year by the use of targeted lethal force outside the United States by remotely piloted aircraft”. The drone casualties so listed would not include those from declared war zones – putting a focus on civilians killed and injured in so-called “shadow battlefields” in places like Pakistan, Yemen and Somalia.

Estimating the number of civilians killed in drone strikes is as difficult as it is contentious. Most observers are hard-pressed to enter places like the tribal regions of Pakistan. Drone strikes are most often reported by anonymous security officials, who have an interest in describing the dead as combatants. Various non-governmental organizations keep estimates of civilian drone casualties – usually in the hundreds, stretching back to the early 2000s – but there is no consensus on a figure, let alone an official statement.

In February, during his nomination hearing to run the CIA, which conducts the majority of US drone strikes, John Brennan signaled an openness to issue a public estimate.

“I believe that, to the extent that US national security interests can be protected, the US government should make public the overall numbers of civilian deaths resulting from US strikes targeting al-Qaida,” Brennan said in responses to prepared questions from the same Senate committee that passed the bill.

The CIA declined to comment on the proposal. Representatives for Dianne Feinstein, the California Democrat who chairs the Senate committee, did not reply to requests for comment by deadline.

The bill also includes an unlikely proposal relating to the most controversial aspect of drone strikes as far as a US audience is concerned: taking steps to avert mistakes in targeting US persons in such strikes.

The bill would require the director of national intelligence to conduct an alternative assessment, known as a “red team analysis”, of the intelligence underlying a determination by any intelligence agency that a US person – a citizen or resident alien – is being considered for “the use of targeted lethal force”. The director would have to notify his inspector general and the congressional intelligence committees that such a determination was made, and would have 15 days to compile the red team analysis.

That analysis would not appear to have the power to override a decision to kill a US person. “Nothing in this section shall be construed to impede the ability of the United States Government to conduct any operation consistent with otherwise applicable law,” the bill reads, although a later section adds: “Nothing in this section may be construed to authorize the use of targeted lethal force against a United States person.”

The US has acknowledged killing four Americans in drone strikes, including the al-Qaida propagandist Anwar al-Awlaki and his 16-year old son, Abdulrahman. Only the elder Awlaki was an intentional target, officials have said, although as yet there has been no restitution made for the apparently accidental deaths.

A different provision of the bill would for the first time extend whistleblower protections to members of the intelligence community, comparable to those enjoyed by other federal employees.

The effort would incentivize future Edward Snowdens to take their concerns about waste, fraud, abuse or illegality inside the 16 intelligence agencies to “the appropriate inspector general of the employing agency, a congressional intelligence committee, or a member of a congressional intelligence committee”, according to the bill text.

Currently, would-be whistleblowers inside the intelligence agencies do not enjoy protections from retaliation. Snowden, the ex-NSA contractor who leaked a trove of documents about the NSA to the Guardian and the Washington Post, has said he had no confidence that internal whistleblower rules within the intelligence community protected him from reprisal.

The proposal still would not do so: it does not apply to contractors. It also mandates internal agency hearings to adjudicate whistleblower disputes, rather than an outside or judicial body. According to Tom Devine, legal director of the Government Accountability Project, this “locks in an institutional conflict of interest”.

But Devine, whose organization advocates for whistleblower rights, hailed the proposal as a “landmark breakthrough”. Previous congressional attempts to extend whistleblower protections to intelligence agency employees have foundered.

“This is not a final solution, but its passage would be a breakthrough paradigm shift for free-speech rights, to challenge abuses of power and corruption in intelligence agencies without risking threats to national security in the process,” Devine said.