The publication of a report into Russian interference in the 2016 Brexit referendum is to be delayed until after the upcoming U.K. general election, Prime Minister Boris Johnson’s office said Monday.

The 50-page report by the U.K. Parliament’s Intelligence and Security Committee, entitled simply “Russia,” was due to be published on Monday.

The culmination of an 18-month inquiry, the report had compiled evidence from Britain’s intelligence agencies and other experts about the extent of Russian interference in Britain’s democratic processes. But it will now not be published until after the Dec. 12 election, after the Prime Minister’s office refused to give the necessary signoff.

“If the Prime Minister has a reason why he can’t publish or doesn’t wish this report to be published, we need to know about it,” Dominic Grieve, the Independent lawmaker who chairs the Intelligence and Security Committee, told Sky News.

A spokesperson for Johnson’s office, 10 Downing Street, brushed off concerns that the report’s delay was political in nature. “There are a number of administrative stages and processes which reports such as this, which often contain sensitive information, have to go through before they are published,” a spokesperson said in a statement.

Russia is suspected of conducting an interference operation to swing the 2016 referendum in favor of the “leave” side, which Johnson supported as a figurehead of the campaign group Vote Leave.

“Delaying publication makes no sense unless there’s something in the report that suggests this election won’t be free and fair,” Kyle Taylor, the director of Fair Vote, a campaign pushing for an independent inquiry into the Brexit referendum, tells TIME. “If there’s nothing we need to be extra conscious of, Dominic Grieve, who has seen it, wouldn’t be pushing for it to be released ahead of the election.”

Grieve, a former Conservative Member of Parliament first elected in 1997, was part of a group of “rebel” lawmakers who voted against Johnson’s Brexit deal in September. He subsequently left the party.

A separate report on disinformation released earlier this year by a U.K. parliamentary committee said that there is “strong evidence” that foreign actors including Russia have attempted to influence U.K. politics. One study referenced in the report found “significant numbers” of articles published by Kremlin-aligned media and promoted on social media during the Brexit referendum, many of which had a “clear anti-E.U. bias.” The report concluded by calling on the U.K. government to conduct an analysis into digital influence campaigns by foreign actors.

“This is the report that would be telling us the actual scale of Russian interference,” Taylor tells TIME. “If this report comes out before the election and it suggests that Russia played a significant role in supporting Vote Leave — i.e. in supporting Boris Johnson — then it could affect him as the leader of the Conservative Party.”

In the same vein, the report would “most certainly affect” the Conservatives’ prospects in the forthcoming election, Taylor argues, “because it could be that thing which finally wakes people up to the idea that Brexit wasn’t free and fair in the first place.”

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Write to Billy Perrigo at billy.perrigo@time.com.