WASHINGTON — Senate Democrats are demanding the Department of Justice disclose the full results of an investigation into whether U.S. Labor Secretary Alexander Acosta is guilty of “professional misconduct” in his handling of a sex crime prosecution against billionaire Jeffrey Epstein over a decade ago.

In a letter obtained by NBC News, Sens. Patty Murray, D-Wash., and Tim Kaine, D-Va., are asking the DOJ to “make public all findings” from its probe into Acosta’s handling, as a former U.S. attorney, of a plea agreement in the Epstein case. The agreement allowed the wealthy financier and philanthropist to plead guilty to lesser charges in state court rather than face federal sex trafficking charges involving more than three dozen underage girls.

Acosta was the U.S. attorney for South Florida in 2007, when federal prosecutors struck a deal that allowed Epstein to plead guilty to two felony charges in state court and ruling out federal charges.

The letter reflects concern on Capitol Hill that the department may not be planning a full public disclosure of all of the details of a highly controversial case involving a Trump Cabinet official — the latest example, many Democrats contend, of an administration that is not committed to transparency around investigations involving its own.

Kaine and Murray note that officials at the DOJ had indicated they would share its results “as appropriate” and “consistent with past practices,” while not committing to sharing a full version with the public. And while they acknowledged DOJ policies that “substantially restrict” public disclosure of its records in general, they contend that standard should not apply to Acosta.

“There must be legitimate oversight by Congress and answers for survivors and the public, particularly when those records concern a present Cabinet official,” the two wrote.

Jeffrey Epstein in 2005. Sipa via AP file

Sen. Ben Sasse, R-Neb, in February initially called for an investigation, after the Miami Herald published a series on Epstein, which raised questions about Acosta’s signing of a non-prosecution agreement despite prosecutors’ drafting of an indictment.

Sasse’s letter prompted a response from Assistant Attorney General Stephen Boyd, acknowledging that the department’s Office of Professional Responsibility was investigating Acosta for professional misconduct.

Typically that office is used to discipline federal attorneys, not to prosecute them.

A spokesman for the Justice Department declined to comment on the letter from Murray and Kaine.

“The investigation is ongoing, and as we indicated in the February 6 response to Senator Sasse, we will share the results of OPR’s results at the conclusion of its investigation as appropriate. Because the matter is ongoing, it would not be appropriate to comment further,” said Wyn Hornbuckle, a Justice Department spokesman.

The demand from Murray and Kaine comes in the wake of Attorney General William Barr’s testimony before Congress this week regarding the Mueller report on the Trump campaign and Russia.

Barr has said he will share the report in the coming days. But he has declined to seek court approval to give Congress access to the full version of the report and has, so far, rejected Democrats demands to see classified portions of the report.

Acosta’s role in the Epstein matter came under increased scrutiny after the Herald reported on a judge’s ruling in February that Acosta and other prosecutors had violated federal law by failing to consult with Epstein’s victims before agreeing to the deal.

Other Trump allies are also implicated in the story. Harvard law professor Alan Dershowitz, who has been a steady defender of Trump on television, has been accused by attorneys for the victims of having sex with underage girls before serving on the legal team that helped broker the Epstein agreement. Dershowitz has adamantly denied the charges.

Lawyers for victims who were sexually abused as minors have formally demanded that the government vacate Epstein’s plea deal and reopen his sex trafficking investigation.

Both Kaine and Murray are on the Senate Committee on Health, Education, Labor and Pensions. Kaine pressed Acosta on the issue during his nomination hearing and ultimately opposed the nomination citing Acosta’s involvement in the case.