On Thursday, Senate Democrats asked the Justice Department’s watchdog to investigate allegations of political interference at the department.

Ten Senate Democrats wrote to Justice Inspector General Michael Horowitz expressing concerns that President Trump and his administration have sought improper influence on the apolitical work of the Justice Department. This comes after four career prosecutors recently withdrew from former Trump adviser Roger Stone case’s (with one resigning) after political appointees overruled their sentencing recommendation following criticism from the president. The move to overrule the recommendation was largely unprecedented and could hinder morale across the career workforce, according to former prosecutors. The letter addressed that and other situations over the last three-years that the lawmakers deem questionable.

“The department’s mission to ‘enforce fair and impartial administration of justice for all Americans’ requires that its prosecutorial decisions be insulated from political influence, including influence from the White House,” wrote Sens. Kamala Harris, D-Calif.; Dianne Feinstein, D-Calif.; Patrick Leahy, D-Vt.; Dick Durbin, D-Ill.; Sheldon Whitehouse, D-R.I.; Amy Klobuchar, D-Minn.; Christopher Coons, D-Del.; Richard Blumenthal, D-Conn.; Mazie Hirono, D-Hawaii; and Cory Booker, D-N.J. “Our concern is that politically motivated enforcement of federal law could become standard practice. This would permanently damage the integrity and independence of the Justice Department.”

The inspector general’s office declined to comment on whether or not it will take up the request or if it will respond to the letter.

Some examples the Senate Democrats claim demonstrated improper influence by the Trump administration are:

Attorney General William Barr named an outside prosecutor to review the career prosecutor’s handling of former National Security Adviser Michael Flynn’s case, which the president has called “unfair” many times.

Former U.S. Attorney for the District of Columbia Jessie Liu was reportedly urged to leave her post and then withdrawn from consideration for a senior Treasury Department position because of her strained relations with Barr after she did not indict Andrew McCabe, former FBI deputy director and a target of the president. Career prosecutors declined to press charges following an allegation that McCabe lied to investigators.

On the July call that was exposed by a whistleblower and sparked the impeachment investigation of Trump, the president said the Justice Department could work with the Ukrainian government on various investigations.

The Office of Legal Counsel, a division of the Justice Department, “provided questionable legal justifications and political cover” for some of the administration's actions, the letter said. One example was a memo that said Trump’s Ukraine call was not an “urgent concern,” which the inspectors general community rebuked.

Special Counsel Robert Mueller’s report on Russian interference in the 2016 election said the president asked then-Attorney General Jeff Sessions several times to “unrecuse” himself from the Russia investigation to prosecute 2016 Democratic presidential nominee Hillary Clinton.

During an interview with ABC News on Feb. 13, Barr said: “the president has never asked me to do anything in a criminal case” and “I will make those decisions based on what I think is the right thing to do and I'm not going to be bullied or influenced by anybody.” However, he said the president’s tweets “make it impossible for me to do my job and to assure the courts and the prosecutors in the department that we're doing our work with integrity.”

On Friday Rep. Jerry Nadler, House Judiciary Committee chairman, wrote a similar letter to Barr with concerns over political interference at the department. He asked Barr to allow the prosecutors who quit the Stone case and other current and former officials to testify before Congress. He also sought documentation and communications on the White House’s involvement with Justice by March 13.

In the aftermath of 1,100 former Justice officials calling on Attorney General Barr to resign on Feb. 16 based on his handling of the Stone case, he is scheduled to testify before the House Judiciary Committee on March 31.

The Justice Department would not comment on either letter.