WASHINGTON — U.S. Sen. Sherrod Brown, D-Ohio, is calling for an independent prosecutor to investigate ties between Russia and President Donald Trump’s associates.

In a conference call with reporters on Wednesday, Brown said that an independent investigation is vital to maintain public trust in the matter, following Trump firing of FBI Director James Comey on Tuesday.

“I’ve spoken with a number of people — Republicans and Democrats, but mostly Republicans — and everyone is concerned with Trump’s ties between Russia, Putin and the oligarchs,” Brown said.

The Trump administration said the firing of Comey was due to his handling of the investigation into former U.S. Sec. of State Hillary Clinton’s email server, but Brown said the timeline of the firing did not fit the explanation.

“If this was about the Clinton campaign, he would have fired him on Jan. 20,” Brown said of the date of Trump inaugural. “He’d said positive things about him before that.”

Brown said the Russian investigation appeared to be the reason for Comey’s firing.

“I think it was pretty clear that Comey was getting closer to information that would embarrass or implicate the Trump Organization,” Brown said.

According to a CNN report, the FBI had issued information to associates of Gen. Michael Flynn, who resigned as Trump’s national security advisor after his ties and contacts with Russia became public.

Brown said that four individuals Trump has fired since his inaugural have been due to the Russian investigation.

“He fired the attorney general (Sally Yates), who was looking into Flynn, Gen. Flynn had connections to the Russian investigation, the U.S. attorney in New York (Preet Bharaha) was looking into things, and now, the FBI director, Brown said.

Brown said he disagreed with Republicans, led by U.S. Sen. Mitch McConnell, who feel the investigation should be left to Congress.

“I don’t understand why it would impede the Senate investigation,” Brown said of the FBI’s effort.  “You don’t shut down the investigation coming from our chief law enforcement arm in the FBI.”

Brown said the investigation need to take place.

“I want it done,” he said. “I don’t want it to take a year.”

He said that a special prosecutor needs to be appointed to restore faith in the effort.

“Nobody in either party really trusts this president to put someone in there who would be fair,” he said of the FBI position.

Brown pointed to former New York Mayor Rudy Giuliani, a backer of Trump’s campaign, who was seen at Trump’s Washington, D.C. hotel on Wednesday and was rumored to have been up for the position before removing his name from consideration.

“That was just laughable,” Brown said, adding that Giuliani would never have achieved confirmation by the Senate.

Brown issued an earlier statement on Tuesday, following Comey’s dismissal, where he said Comey had been “marred by questionable judgment,” but wanted to know more about the reasons behind his removal.

“At the same time, the President firing the FBI Director in the middle of an investigation into the White House’s ties to Russia raises serious questions about the independence of the FBI and the integrity of the ongoing investigation,” Brown said. “The President must nominate a replacement with an independent record that is beyond reproach. Now, more than ever, we need an independent investigation into Russian ties to ensure the American people can have full confidence in the findings.”

Brown’s Republican counterpart from Ohio, U.S. Sen. Rob Portman, called for an explanation of the firing and focused on his thoughts on Comey’s replacement.

“I want to thank Director Comey for his service to our country,” Portman said in a statement on Tuesday. “Regardless of his handling of the Clinton email matter during the presidential election last year — for which both parties had questions and concerns — he has always done what he believed was in the best interest of the country. Given the timing and circumstances of the decision, I believe the White House should provide a fuller explanation regarding the president’s rationale. The American people must have faith in a strong, independent FBI. I’m concerned about eroding trust in this premier law enforcement agency. It is important that whoever is nominated to succeed

Director Comey is a highly-qualified and respected leader who will provide a fresh start for the bureau.”