Whistleblowers’ names will not be disclosed by a private watchdog group that set up its own hotline for insiders to help expose wrongdoing at the Department of Veterans Affairs, the head of the nonprofit Project on Government Oversight said Friday.

POGO let the deadline pass Friday morning without turning over the detailed records sought by the VA's inspector general, which is investigating reports nationwide that secret wait lists were kept and documents were falsified to hide backlogs in delivering medical care at veterans' hospitals.

Revealing the identities of whistleblowers who took their information to POGO would send a “chilling message to anyone who might speak out about corruption or mismanagement within VA,” said Danielle Brian, the group’s executive director.

But acting Inspector General Richard Griffin made it clear he will not back down in an exchange of letters with Sen. Tom Coburn, R-Okla., a longtime advocate of whistleblower protection laws, who intervened on POGO's behalf.

“Because the VA OIG is the only entity that has the statutory authority to obtain all records and interview all the individuals to verify or refute allegations, we sought information from POGO to include in our investigation,” Griffin said Friday in a letter to Coburn. “It is irresponsible for any private organization, such as POGO, to report mere allegations as fact without conducting a complete and thorough investigation.”

Also Friday, acting VA Secretary Sloan Gibson sent an email to agency employees saying he would not tolerate retaliation against whistleblowers.

“I expect employees to bring to the attention of their managers and supervisors shortcomings in the delivery of our services to Veterans or any perceived violations of law or official wrongdoing — including gross waste, fraud or abuse of authority,” Gibson said. “And I want to make clear that intimidation or retaliation against whistleblowers is absolutely unacceptable. I will not tolerate it.”

The latest scandal at the VA erupted in April when allegations surfaced during a House committee hearing that a secret wait list was used at the veterans' hospital in Phoenix to falsely make it appear patients seeking medical appointments were being seen within agency deadlines.

An interim report released last month by the IG found “systemic” manipulation of reported wait times to hide long delays at VA medical centers nationwide. The investigation has spread to more than 70 VA facilities, Griffin said in his letter to Coburn.

POGO and the group Iraq and Afghanistan Veterans of America created their own whistleblower site, launched May 15, as a safe place for people to expose wrongdoing at the VA.

POGO had received 700 tips as of this week, about a fourth of them from VA employees.

The IG issued its subpoena May 30, the same day then-Secretary Eric Shinseki resigned in the fallout over the Phoenix investigation.

The Washington Examiner and other media have reported that VA whistleblowers routinely face retaliation ranging from harassment to firing. Many whistleblowers who have helped expose the underhanded practices at VA hospitals say the retaliation came after they tried to report their allegations to the inspector general.

Dr. Sam Foote, the former Phoenix VA doctor who is the main whistleblower there, took his complaints to the IG in 2011 and again in 2013, Coburn said in his letter asking Griffin to explain why he would subpoena an independent watchdog willing to protect the confidentiality of agency employees.

The IG launched its investigation after being directed to do so in April by Rep. Jeff Miller, R-Fla., chairman of the House Committee on Veterans’ Affairs. Miller said at the time as many as 40 patients died as a result of delays in care while waiting on the secret list.

The government has tried unsuccessfully to force POGO to disclose confidential information in the past. The group has never complied, Brian said.

“It’s not going to happen now,” she said.

Coburn weighed in on POGO’s behalf Thursday. He said in his letter to Griffin that he is “troubled by the timing of this administrative subpoena,” and that it could discourage other whistleblowers who fear retaliation from coming forward.

“VA needs more whistleblowers to come forward to assist in learning what happened,” Coburn said. “Unfortunately, the timing of this subpoena may have a negative impact on these voices coming forward. Voices that the public needs to hear from.”

The overriding issue for POGO is that it cannot effectively function as an independent watchdog if it cannot protect confidential informants from having their names disclosed to the government, said Joe Newman, spokesman for the nonpartisan organization. Beyond that, the law makes it clear that the IG has the discretion to disclose the name of a whistleblower if it is deemed “unavoidable during the course of the investigation.”

But Griffin dismissed POGO’s claims it can use First Amendment protections to protect whistleblowers who have contacted the organization, an argument usually raised by the news media.

Federal courts in D.C. have “long held that a subpoena will be enforced regardless of potential First Amendment issues, where the agency seeking the information is conducting an investigation pursuant to its statutory authority,” Griffin said in his letter to Coburn.

Griffin also revealed in the letter that his investigators have conducted hundreds of interviews, are reviewing more than 1 million emails, and have received more than 10,500 complaints on its tip line since the Phoenix scandal broke.

“Numerous members of Congress established hotlines within their districts and have been referring the complaints on a daily basis to my office without redacting the names of the complainants,” Griffin told Coburn.

IG investigators are working with the FBI to investigate potential felony criminal conduct, including alteration of government records or impeding a federal investigation, Griffin said.