WASHINGTON — Two Republican House committee chairmen are calling for a new special counsel to take a broad look at whether Justice Department or FBI employees were biased as they began investigating President Donald Trump’s ties to Russia in 2016 and whether there were surveillance abuses as part of that probe.

Reps. Robert Goodlatte of Virginia and Trey Gowdy of South Carolina wrote Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein on Tuesday to ask for the new special counsel, whose work would be separate from special counsel Robert Mueller’s investigation into Trump and Russia.

Republicans have alleged surveillance abuses in the department, releasing a declassified memo last month that detailed the use of political opposition research to obtain a warrant to monitor a former adviser to Trump’s campaign.

Republicans have alleged surveillance abuses in the department, releasing a declassified memo last month that detailed the use of political opposition research to obtain a warrant to monitor a former adviser to Trump’s campaign. Democrats countered with their own memo that said the FBI only “made narrow use” of that research paid for by Democrats.

Goodlatte is chairman of the House Judiciary Committee and Gowdy is chairman of the House Oversight and Government Reform Committee. Gowdy is also on the Judiciary panel.

“With respect to potential and actual conflicts of interest, decisions made and not made by both former and current Department of Justice and FBI officials have led to legitimate questions and concerns from the people whom we all serve,” the two men wrote. “There is evidence of bias, trending toward animus, among those charged with investigating serious cases.”

Republicans on the Judiciary Committee have also asked for a special counsel to investigate the decisions surrounding the FBI’s now-closed investigation of Hillary Clinton’s emails.

MORE: What Rick Gates’ plea deal means for the Russia probe

Gowdy did not join in the Clinton request, but said Tuesday that he believes it is important for an independent investigator to look into the surveillance. He said Congress doesn’t have “the tools or the public confidence” to do an investigation on its own. He said a special counsel could look into potential criminal issues, such as whether FBI agents made any misrepresentations to the secret court as it sought the warrant on the Trump adviser, Carter Page.

So far, Sessions has not made a commitment to appoint any additional special prosecutors. He recused himself from the Russia investigations at the beginning of his tenure, and Rosenstein appointed Mueller. Sessions has already asked the department’s own inspector general to look into the questions about surveillance abuses raised by Congress, but it’s not clear what will come of that.

In response to the letter Tuesday, the Justice Department referred to a letter it had sent to Congress several months ago saying Sessions had directed senior federal prosecutors to look into other matters raised by Republicans in Congress, including an Obama-era uranium deal and Clinton’s foundation. The department did not say if Sessions would appoint another special counsel to look into the issues raised by Gowdy and Goodlatte.

Democrats immediately pushed back on the request.

“In this case, it is difficult to see what crime the Republicans are alleging,” said Rep. Elijah Cummings of Maryland, the top Democrat on the oversight panel.

Associated Press Writer Eric Tucker contributed to this report.