Story highlights Booker is among Democrats calling on the appointment of a special prosecutor in Russia investigation

White House says Comey's firing has nothing to do with the ongoing investigation

Washington (CNN) Sen. Cory Booker -- who said he has a "serious problems" with former FBI Director James Comey -- is among the Democratic leaders who find President Donald Trump's firing of the official "very problematic.

"The fact that we have the President of the United States firing someone who has an active investigation on them erodes the public trust," Booker, of New Jersey, said Wednesday on CNN's "Erin Burnett OutFront."

"I've been one of those people with serious problems with Comey ... but this is very problematic," Booker said.

Booker's comments came one day after Trump -- acting on a letter from Deputy Attorney General Rod Rosenstein -- shocked Washington by firing Comey, the man responsible for the bureau's investigation to possible ties between Trump campaign associates and Russia.

White House officials -- including senior adviser Kellyanne Conway and deputy press secretary Sarah Huckabee Sanders -- have maintained that Trump's decision to let Comey go doesn't have anything to do with the current ongoing investigation into Russia's interference into the 2016 election.

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