No 10 has dismissed as “vexatious” a freedom of information request by the Bureau for emails between the prime minister’s office and the parliamentary committee behind the Russia report in the run up to the 2019 general election.

The Bureau sought these emails because they could have shed light on Boris Johnson’s controversial decision to delay the publication of the Intelligence and Security Committee (ISC) report into Russian influence in the UK until after the election.

Downing Street refused the FOI request by dismissing it as “vexatious”, a rarely used refusal reserved for requests which were “disproportionate or unjustified level of disruption, irritation or distress”.

The documents could have been collated by No 10 via a series of simple searches.

“Boris Johnson has been accused by his critics of a ‘cover-up’ by blocking the release of the Russia report. Blocking the publication of correspondence around that decision could look like a cover-up of the cover-up,” said Rachel Oldroyd, the Bureau’s managing editor.

“The Bureau has only ever been interested in securing the report – and scrutinising the decision to block it – in the spirit of informing the public and keeping government transparent. This decision threatens those goals.”

The rules on reports from the ISC allow the prime minister time to suggest additional redactions beyond those requested by the security services. The convention is that this is ten days.

In the run up to the 2019 general election, the ISC’s staff made arrangements to ensure the report could be published in as little as an hour if No 10 gave permission to do so. However, shortly before the election Johnson claimed the government needed more time to scrutinise it. At the time Dominic Grieve, then the ISC chairman, said the decision to delay its publication was “jaw-dropping”.

Johnson came under fire during the campaign for refusing to green light the publication of the report. According to press reports, the ISC report could contain information that is potentially embarrassing for the Conservative party.