President’s decision to have US intelligence agencies look over evidence comes after unrelenting pressure from Democratic lawmakers to declassify information

Barack Obama has ordered US intelligence to review evidence of Russian interference in the 2016 presidential election after coming under sustained pressure from congressional Democrats.

The review will be one of Obama’s final instructions to the intelligence agencies, which will soon report to Donald Trump, whom congressional Democrats consider the beneficiary of a hack targeting the Democratic National Committee.

Lisa Monaco, the White House counterterrorism director, announced what she called a “full review” at a breakfast briefing sponsored by the Christian Science Monitor on Friday.

At the White House press briefing later on Friday, Eric Schultz, the deputy White House press secretary, denied the review was “an effort to challenge the outcome of the election”.

“We have acknowledged who won the election,” he said. “It wasn’t the candidate the president campaigned for. He has gone out of his way to ensure a smooth transition of power.”

The review will span the last three presidential election cycles, Schultz told reporters. “These agencies will have to take a look at what we saw in 2008, 2012 and 2016. This is going to be a deep dive. This is a review that will be broad and deep at the same time. They’re going to look at where the activity leads them to look at.”

There were intrusions into both the Obama and John McCain campaigns in 2008, publicly attributed to the Chinese, he continued, and although there were no notable incidents in 2012, “knowing what we know now”, that election will also be scrutinised.

In 2016, he said, the government did not detect any increased cyber activity on election day itself but the FBI made public specific acts in the summer and fall, tied to the highest levels of the Russian government. “This is going to put that activity in a greater context ... dating all the way back to 2008.”

Asked if the review would investigate Russia’s motives, Schultz replied: “Malicious cyber activity, specifically malicious cyber activity tied to our elections, has no place in the international community. Unfortunately this activity is not new to Moscow. We’ve seen them do this for years ... The president has made it clear to President Putin that this is unacceptable.”

Obama expected the review to be completed before he leaves office, Schultz said. “This is a huge priority ... I think the president wanted this done under his watch because he takes it very seriously. This is something the president has been watching closely for eight years now.”

Schultz also told the briefing: “We’re going to make public as much as we can. As you can imagine, something like this might include sensitive and even classified information. When that report is submitted we’re going to take a look. We want to brief Congress and the relevant stakeholders, possible state directors.”

“This is good news. Declassifying and releasing information about the Russian government and the US election, and doing so quickly, must be a priority,” said Ron Wyden, an Oregon Democrat on the Senate intelligence committee.

In October, the director of national intelligence and the secretary of homeland security publicly accused the “senior-most” levels of the Russian government of directing those digital breaches. Trump, who has treated Russian president Vladimir Putin with a warmth unequalled by most US politicians, has repeatedly dismissed the accusation as politically motivated.

US intelligence laid the blame for the DNC hack at Russia’s feet but has not provided evidence supporting the accusation, although several private cybersecurity firms reaching the same conclusion have. Earlier this month, all the Democratic members of the Senate intelligence committee publicly intimated the administration knows significantly more about Russian culpability than the October statement revealed, and implored Obama for a public disclosure he has thus far resisted.

Yet the White House was more sympathetic to a request earlier this week from several senior Democrats in the House of Representatives, who wrote to Obama requesting a classified briefing on the role the Russians played in the election.

While Democrats, stung by a rout in an election many expected to win, have spearheaded the calls for disclosure of Russian interference, they also have some Republican support. Lindsey Graham, the South Carolina hawk who savaged Trump on the campaign trail, told CNN this week he will use his Senate perch to pursue an investigation of Russian involvement in the DNC hack.

According to Monaco, the review will be classified and delivered to lawmakers before Obama leaves office on 20 January.

Democrats immediately pounced on the announced review and pressed the White House to declassify it before Trump takes office.

Adam Schiff, the top Democrat on the House intelligence committee, said Russia had “succeeded” in “sow[ing] discord” in the election, and urged as much public disclosure as is possible.

“More than that, the administration must begin to take steps to respond forcefully to this blatant cyber meddling, and work with our allies in Europe who have been targets of similar attacks to impose costs on the Kremlin; if we do not, we can expect to see a lot more of this in the near future,” Schiff said Friday.

A spokesman for the director of national intelligence declined to comment.