The Republican-led House intelligence committee on Friday officially declared the end of its Russia investigation, saying in its final report that it found no evidence that the Trump campaign colluded with Russia in the 2016 presidential election.

The report’s conclusion is fiercely opposed by Democrats on the committee, who say the panel did not interview enough witnesses or gather enough evidence.

The investigation began with bipartisan promise but ultimately succumbed to factional squabbling. Republicans had already announced the main findings last month. An investigation led by special counsel Robert Mueller is ongoing, as are investigations led by the Senate intelligence and judiciary committees.

The House panel did find that Russia sought to sow discord in the US through cyberattacks and social media. Some portions of the report are redacted for national security reasons. Republicans say they will pressure intelligence agencies to be able to release more information.

Mike Conaway of Texas, who has been leading the investigation, said he was “extremely disappointed with the overzealous redactions” made by the intelligence agencies. Many of the blacked out details include information already public such as witness names and previously declassified information, he said.

Conaway said the committee had pledged to be “as transparent as possible”, adding: “I don’t believe the information we’re releasing today meets that standard, which is why my team and I will continue to challenge the [intelligence community’s] many unnecessary redactions with the hopes of releasing more of the report in the coming months.”

Adam Schiff, the ranking Democrat on the committee, issued a scathing statement. Republicans, he said, had “a fundamentally flawed approach to the investigation”, the conclusions of which he said were “superficial and political”.

The California Democrat went on: “Throughout the investigation, committee Republicans chose not to seriously investigate – or even see, when in plain sight – evidence of collusion between the Trump campaign and Russia, instead adopting the role of defense counsel for key investigation witnesses.”

Trump has repeatedly said there was “no collusion”. On Friday, he tweeted: “Just Out: House Intelligence Committee Report released. ‘No evidence’ that the Trump Campaign ‘colluded, coordinated or conspired with Russia’. Clinton Campaign paid for Opposition Research obtained from Russia– Wow! A total Witch Hunt! MUST END NOW!”

Trump later spoke to reporters in the Oval Office, where he was meeting German chancellor Angela Merkel. The president called the report “very good” and “totally conclusive”.

“No collusion, no coordination, no nothing,” he said. “It’s a witch hunt. That’s all it is. There was no collusion with Russia.”

He then said: “The report was very powerful, very strong.”

The New York Times reported, meanwhile, that the Russian lawyer who met Donald Trump Jr, Jared Kushner and Paul Manafort at Trump Tower in June 2016, promising compromising information on Hillary Clinton, has closer ties to the Russian government than she has previously admitted.

Natalia Veselnitskaya reportedly told NBC News in an interview to be broadcast on Friday she was “a lawyer and … an informant” for Russia’s prosecutor general.