It is "almost certain" Russia tried to interfere in last year's general election by leaking Government documents, the Foreign Secretary has said.
In a written Commons statement, Mr Raab said a criminal investigation is underway into the "illicitly acquired" documents.
The papers were highlighted by Jeremy Corbyn in the build up to the election.
The then-Labour Party leader used the material, concerning UK and US trade talks, to reinforce his claims that the Conservatives were preparing to "sell off" the NHS.
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Mr Rabb said in the statement: "On the basis of extensive analysis, the Government has concluded that it is almost certain that Russian actors sought to interfere in the 2019 general election through the online amplification of illicitly acquired and leaked Government documents.
"Sensitive Government documents relating to the UK-US free trade agreement were illicitly acquired before the 2019 general election and disseminated online via the social media platform Reddit.
"When these gained no traction, further attempts were made to promote the illicitly acquired material online in the run-up to the general election."
After Labour pointed out the documents at a November press conference, online discussion site Reddit said its own investigation had linked the appearance of the papers to a previous Russian disinformation campaign.
It is believed the material had appeared online some months earlier but attracted little attention until they were picked up by the Labour campaign.
Mr Raab’s statement comes after the new parliamentary Intelligence and Security Committee (ISC) was formed.
At its first meeting, the ISC agreed it would publish a long-awaited report into Russian interference in UK politics before Parliament’s summer recess.
The official spokesman for the Prime Minister dismissed "nonsense" suggestions that Mr Raab’s statement was timed to pre-empt the report.
A Labour spokesman said: “We condemn any attempt by Russia, or any foreign power, to interfere in our country’s democratic processes.
"Labour stands ready to work cross-party to protect our nation’s security. That includes in our response to the publication of the long-awaited report by the Intelligence Security Committee on the Russian threat to the UK."
Meanwhile the National Cyber Security Centre (NCSC) has warned that hackers linked to Russian intelligence agencies are targeting British scientists seeking to develop a COVID-19 vaccine.
The NCSC, together with the US National Security Agency and the Canadian Communication Security Establishment, said the attacks were part of a global campaign by the group known as 'APT29' to steal the secrets of research into a vaccine.
The NCSC said it, together with its US and Canadian associates, assessed APT29 was "almost certainly" operating as part of the Russian intelligence services.
NCSC director of operations, Paul Chichester, said: “We condemn these despicable attacks against those doing vital work to combat the coronavirus pandemic.
“Working with our allies, the NCSC is committed to protecting our most critical assets and our top priority at this time is to protect the health sector.
“We would urge organisations to familiarise themselves with the advice we have published to help defend their networks.”
Mr Raab described the news as "completely unacceptable".
Cover image: PA.