House Democrats slammed their Republicans colleagues Thursday for issuing 17 subpoenas and sending 54 letters in pursuit of information related to Hillary Clinton's private email server.

Rep. Elijah Cummings, ranking Democrat on the House Oversight and Government Reform Committee, called the congressional investigation a "desperate onslaught of frivolous attacks."

"House Republicans have focused more on their obsession with bringing down Secretary Clinton than on any other issue facing Congress," Cummings said in a statement. "This is an outrageous abuse of taxpayer dollars for partisan political purposes, particularly when Republicans are ignoring so many pressing issues facing the American people."

Democrats have frequently objected to the GOP oversight efforts that followed FBI Director James Comey's controversial decision in July to close his year-long probe of Clinton's private emails without recommending indictments for anyone involved.

House Minority Whip Steny Hoyer noted that "investigation after investigation has found no wrongdoing," although an inspector general probe of email practices implemented by past secretaries of state faulted Clinton for subverting agency rules, and the FBI determined she engaged in "extreme carelessness" by routing sensitive material through a private server.

Rep. Jason Chaffetz, R-Utah, who chairs the committee, has held four public hearings and one classified session related to Clinton's emails this month. Two additional hearings — one examining the Justice Department's handling of immunity agreements and one gauging the progress of the State Department's efforts to turn over requested documents — were postponed in the past week.

Chaffetz sent his most recent letter on Wednesday to an attorney for Platte River Networks, the technology firm tapped to manage Clinton's email network in 2013.

Employee Paul Combetta and CEO Treve Suazo both received subpoenas from the committee, records released by House Democrats show. The letter to Platte River's representation Wednesday indicated the committee intends to "consider all its options to enforce the subpoenas."

Documents indicate Chaffetz has demanded records or testimony from 25 people associated with the Clinton email case, including from Clinton Foundation President Donna Shalala and Reddit's general counsel, Melissa Tidwell.

The Utah Republican asked Shalala to provide copies of all emails sent between the State Department and the foundation during Clinton's tenure, as well as invoices that might shed light on the travel expenses that Huma Abedin and Cheryl Mills, two top Clinton aides, might have incurred on the foundation's dime.

Chaffetz wrote to Reddit's representation on Sept. 21 and asked the popular online forum to preserve posts that may have been authored by Combetta or other individuals involved with the destruction of Clinton's emails.

Combetta, who received an immunity agreement from the Justice Department during the FBI's investigation, is believed to have asked fellow Reddit users how to "strip out" Clinton's email address from records he was preparing to turn over to her legal team ahead of their production of 30,000 emails to the State Department in Dec. 2014.

Democratic criticism of GOP oversight efforts in the Clinton email case has mirrored criticism of the Benghazi investigation, which wound down earlier this year. For more than a year, minority members have accused Republicans of engaging in wasteful partisan exercises when their probes have turned to issues that fell under Clinton's purview as secretary of state.

During the Benghazi investigation, Cummings and his staff occasionally released documents related to Clinton in an attempt to prevent leaks from damaging the Democratic nominee.

Several of the letters and subpoenas published Thursday had not yet been made public by congressional Republicans.