"There's absolutely no evidence that I've ever seen of any Russian interference in UK democratic processes," Johnson said, when asked about a dossier on alleged Russian interference.
The prime minister added that he saw no reason to change the publication schedule of the report in question.
Johnson was making a campaign appearance at an engineering company in Stockton-on-Tees ahead of the December general election.
Last week, security minister Brandon Lewis said that the UK government will publish its parliamentary report on “Russian meddling” in the Brexit vote after the December 12 election.
The results of an 18-month inquiry by the House of Commons intelligence and security committee into allegations of Russian interference in the 2016 Brexit vote were expected to become public.
The government is keeping the dossier, which has already been approved by the intelligence community, under wraps, saying that it would take six weeks to ensure whether it contains no classified information. The release was rescheduled until after the 12 December general election, in a move which opposition lawmakers called politically motivated.