More journalists, transparency advocates and individuals sued the State Department over unanswered open records requests in 2015 than any year in the past decade. Hillary Clinton's emails played a role.

While the number of Freedom of Information Act lawsuits filed against the federal government overall rose only slightly between 2014 and 2015, the number of lawsuits filed against the State Department nearly doubled, according to data compiled by the Transactional Records Access Clearinghouse at Syracuse University.

Rep. Jason Chaffetz, chairman of the House Oversight and Government Reform Committee, blasted the State Department on Tuesday for its "blatant disregard" of rules that dictate how federal agencies should handle requests for documents.

"The department's posture with respect to FOIA compliance has resulted in a dramatic increase in costly litigation," Chaffetz wrote in a letter to Secretary of State John Kerry Tuesday.

He said the agency's "FOIA operation drains the resources of the Department's entire FOIA program by causing staff to run repeated searches, respond to unnecessary appeals requests, and handle increased inquiries from the requesters."

State officials fought 30 lawsuits in 2014, but were hit with 54 lawsuits in 2015, Syracuse University's FOIA Project found. The agency spent more than $2 million fighting legal battles over FOIA in 2014, Chaffetz noted.

The explosion of transparency litigation last year coincided with a national controversy over Hillary Clinton's private emails.

Several high-profile cases involving Clinton's emails dealt victories to FOIA requesters and defeats to the State Department, which spent taxpayer money fighting the dozens of lawsuits in federal court last year.

That included a FOIA case filed by Jason Leopold, a reporter for Vice News, that forced the State Department to release all 55,000 pages of Clinton's emails on a rolling basis between May 2015 and Jan. 2016. The production is still not completed.

In court documents filed in various FOIA lawsuits, the State Department blamed its slower FOIA responses on the influx of new requests related to Clinton's private emails. The existence of her secret server was first made public in March, leaving months for journalists, watchdog groups and individuals to put together cases against the State Department.

The federal government was sued 498 times last year, a small spike over the 421 lawsuits agencies faced in 2014.

The State Department has not yet made its 2015 FOIA report public, although the agency was required to submit that report to the Department of Justice by Dec. 4. All federal agencies should have submitted a review of their FOIA compliance to the Department of Justice by that date.

A Justice Department official told the Washington Examiner the agency planned to begin making those reports public Tuesday and continue rolling them out over the next several weeks.

But a review of the State Department FOIA reports filed at the end of each quarter of 2015 indicate the agency received 18,437 FOIA requests last year alone.

As big as that number may seem, the State Department actually received more requests the year before, accepting 19,625 records requests in 2014.

That means more requesters sued the State Department over fewer FOIA requests last year.

Transparency advocates have criticized the State Department for its handling of FOIA requests related to Clinton's emails, arguing the agency has been intentionally evasive when responding to questions about the former secretary of state's emails.

Indeed, the backlog of FOIA requests grew significantly last year. At the end of 2014, the State Department had 10,965 records requests waiting for an answer. That backlog had jumped to 14,489 by the end of 2015.

In his letter to Kerry Tuesday, Chaffetz demanded documentation of all lawsuits filed against the State Department over the past 15 years, with a special focus on FOIA requests that had sought records from the secretary of state's office.