The FBI covered up information about Russia seeking to tip the 2016 presidential election in Donald Trump’s favour, a senior Democrat claimed on Saturday, after reports emerged about spy agencies’ investigations into hacks of US political parties.

Harry Reid, outgoing Senate minority leader, compared FBI director James Comey to the agency’s notorious founder, J Edgar Hoover, and called for his resignation.

A secret CIA analysis found that people with connections to the Russian government provided emails, hacked from the Democratic National Committee and Hillary Clinton’s campaign, to the whistleblower website WikiLeaks in the final months of the election, according to a Washington Post report published late Friday.

“The FBI had this material for a long time but Comey, who is of course a Republican, refused to divulge specific information about Russia and the presidental election,” Reid told MSNBC’s AM Joy on Saturday. Comey testified to Congress in July that he was no longer a registered Republican, though he belonged to the party most of his life.

“Everyone should know WikiLeaks was involved from the very beginning,” Reid continued. “They leaked the information as if it was run by one of the great political operatives in America when in fact it was run by the political operatives in Russia.

“Russia has a pretty good way of cheating. Look at what they did with athletes,” he added, alluding to the long-running doping scandal of Russian Olympic athletes.

Pressed on whether he believed Comey had information on Russia’s influence and sat on it, Reid replied: “That’s right, that is true.”

“I am so disappointed in Comey. He has let the country down for partisan purposes and that’s why I call him the new J Edgar Hoover, because I believe that,” Reid added, calling for the director’s resignation.

“I think he should be investigated by the Senate. He should be investigated by other agencies of the government including the security agencies because if ever there was a matter of security it’s this … I don’t think any of us understood how partisan Comey was.”

Comey had previously angered Democrats when, 10 days before election day, he sent a letter to Capitol Hill leaders indicating the FBI had located additional emails potentially related to its investigation of Clinton’s private email server. Two days before the election, he sent another letter saying the review was complete and that he stood by the bureau’s original conclusion finding no criminal wrongdoing.

A month before the election, the US government formally accused Russia of a campaign of cyber-attacks against Democratic party organisations, with an intention to interfere in the US election. Intelligence officials did not specify that a Trump victory was the ultimate goal at the time. On Friday, Barack Obama ordered a review of evidence that Russia had interfered in the election.

Gene Sperling, a former national economic adviser to Obama and former president Bill Clinton, tweeted: “So at end of close election, FBI deeply hurt HRC [Clinton] based on no evidence, while CIA sat on clear evidence of Putin interference for Trump.”

On Saturday Adam Schiff, the ranking member of the House committee on intelligence, said in a statement that though he could not “comment on or confirm any intelligence briefings … one would also have to be wilfully blind not to see that these Russian actions were uniformly damaging to Secretary Clinton and helpful to Donald Trump.”

He added: “I do not believe this was coincidental or unintended.”

Trump himself curtly dismissed the reports of the CIA findings. “These are the same people that said Saddam Hussein had weapons of mass destruction,” his transition team said in a statement. “The election ended a long time ago in one of the biggest electoral college victories in history. It’s now time to move on and ‘Make America Great Again’.”

The comment earned widespread derision. David Axelrod, a former top adviser to Obama, tweeted that Trump’s “blithe dismissal only deepens concern”, and John Dean, the former White House counsel under former president Richard Nixon, described the response as “remarkably inadequate”. Dean called for the intelligence report on Russia’s role to be made available to the 538 members of the electoral college before 19 December, when they formally vote to elect the next president.

Senior Democrats demanded a congressional investigation next year. “Reports of the CIA’s conclusion that Russia actively sought to help elect Donald Trump are simultaneously stunning and not surprising, given Russia’s disdain for democracy and admiration for autocracy,” said Chuck Schumer, Reid’s successor as Senate minority leader.

“The silence from WikiLeaks and others since election day has been deafening. That any country could be meddling in our elections should shake both political parties to their core.”

Schumer threw down a gauntlet to Republicans to back the investigation. “It’s imperative that our intelligence community turns over any relevant information so that Congress can conduct a full investigation.”

The call poses a dilemma for Republicans who have increasingly rallied around Trump and do not want to be seen undermining his legitimacy. Trump has repeatedly praised Russian president Vladimir Putin and rejected the intelligence community’s findings. In a recent interview with Time magazine, he said: “I don’t believe they interfered. It could be Russia. And it could be China. And it could be some guy in his home in New Jersey.”

In its report on the CIA conclusions, the Post quoted an unnamed senior US official who had been briefed on the intelligence agency findings. “It is the assessment of the intelligence community that Russia’s goal here was to favour one candidate over the other, to help Trump get elected,” the official said. “That’s the consensus view.”

CIA agents told senators it was “quite clear” that putting Trump in the White House was Russia’s goal, according to officials who spoke to the Post.

Meanwhile, a New York Times report suggested that the Republican National Committee was also hacked. “We now have high confidence that they hacked the DNC and the RNC, and conspicuously released no documents” from the RNC, the Times quoted one senior administration official as saying.

A senior administration official told Reuters: “That was a major clue to their intent. If all they wanted to do was discredit our political system, why publicise the failings of just one party, especially when you have a target like Trump?”

The Kremlin has denied accusations of interference in the US election. WikiLeaks founder Julian Assange has denied links with Russia’s government.

At the White House on Friday, deputy press secretary Eric Schultz said Obama had called for the cyber-attacks review, for release before inauguration day on 20 January, to ensure “the integrity of our elections”.

“We are going to make public as much as we can,” Schultz said. “This is a major priority for the president.”

Michael McFaul, former US ambassador to Russia, said that during the election, Republicans had wanted to “avoid the subject altogether and the Obama administration did not want to appear to be influencing the election”.

“Now that the election is over, we need a serious , independent, bipartisan investigation to know the facts.”

Bruce Riedel, a 30-year veteran of the CIA, now director of the Brookings Intelligence Project, called the situation “unprecedented”.

“A foreign adversary has been caught trying to influence an American election. The intelligence community must have certainty that the evidence is concrete to support the conclusion. But revealing the evidence may not be in the national interest and undermine future capabilities to monitor Russia’s next attack on the nation.”