WASHINGTON — Former FBI Director James Comey was grilled for more than six hours Friday behind closed doors at a congressional hearing – but Republicans are calling him back for more.

“We had more questions than we had time,” said Rep. Trey Gowdy (R-S.C.), the chairman of the House Oversight Committee.

Comey agreed to return Dec. 17, but questioned what more Republicans would want to know.

“After a full day of questioning a few things are clear to me. One — we could have done this in open setting,” Comey said.

“And two — when you read the transcript you’ll see that we’re talking again about Hillary Clinton’s emails for heaven’s sake. So I’m not sure we need to do this at all.”

Democrats charged that summoning Comey was the GOP’s final attempt to distract from special counsel Robert Mueller’s Russia probe before they lose control of the House in January.

“This is a big wild goose chase,” said Rep. Raja Krishnamoorthi (D-Ill.) “It reinforced my view that the Clinton probe has fully run its course.”

Rep. Jerrold Nadler (D-NY) said he plans to shut down the GOP inquiry once he becomes chairman of the Judiciary Committee.

“It’s a waste of time to start with,” Nadler said. “The entire purpose of this investigation is to cast dispersion on the real investigation (by) Robert Mueller. There’s no evidence whatsoever of bias at the FBI.”

But Rep. Darrell Issa (R-Calif.) accused Comey’s FBI lawyer of preventing him from being forthcoming – a notion that was rejected by Democrats, Comey and at least one Republican.

“One of the disappointments of this deposition so far has been the amount of times in which the FBI believes that Congress doesn’t have a right to know,” Issa told reporters.

He added: “The Department of Justice is going to have to agree to allow him to come back and answer a great many questions that currently he is not answering.”

Comey’s interview came as GOP lawmakers are wrapping up a yearlong investigation into decisions made at the Justice Department during the 2016 presidential election.

Republicans say department officials were biased against President Donald Trump as they started an investigation into his campaign’s ties with Russia and cleared Clinton in a separate investigation into her email usage.

Comey was in charge of both those investigations.

Rep. Mark Meadows (R-N.C.) said Comey’s FBI lawyer pushed back on questions on the ongoing Mueller probe, which was “consistent” with past congressional interviews.

“The FBI attorney is not engaging any more or any less than what she has done in previous transcribed interviews,” Meadows, a Trump ally, said. “So I don’t know if there’s really a breaking news story there.”

Comey defended the Mueller probe as important and said it is being handled “very professionally.” He rejected the GOP’s claims that the Justice Department improperly sought surveillance on a Trump campaign adviser, Carter Page, to launch the Russia probe.

“I have total confidence that the FISA process was followed and the entire case was handled in a thoughtful responsible way by DOJ and the FBI,” Comey said of the foreign surveillance court. “I think the notion that FISA was abused here is nonsense.”

While Comey praised Trump’s nominee for attorney general, William Barr, he blasted Trump’s repeated public gripes with the justice system.

“The president’s attacks on the Justice Department broadly and the FBI are something that — no matter what political party you’re in — you should find deeply troubling,” Comey said.

Trump took to Twitter to slam his former FBI chief.

“It is being reported that Leakin’ James Comey was told by Department of Justice attorneys not to answer the most important questions. Total bias and corruption at the highest levels of previous Administration. Force him to answer the questions under oath!” Trump wrote.

Comey has been under fire for using his personal Gmail for government business – while investigating Clinton for her private email misuse. The Post exclusively reported in November that Comey used private email for FBI business many times.

The Post asked Comey on Friday why he used his personal email for government business.

“I’m not going to go into that,” he said.