Downing Street has been accused of sitting on an explosive parliamentary report on the security threat posed by Russia to the UK, which examined allegations that Kremlin-sponsored activity distorted the result of the 2016 EU referendum.

The cross-party intelligence and security committee said it had expected Boris Johnson to approve publication of the 50-page dossier by Thursday – and there was now a risk its publication would be prevented before the general election.

Dominic Grieve, who chairs the committee, complained in the Commons that no explanation for the “apparent delay” had been given by Downing Street, which had been sent a final draft of the report on 17 October.

If Downing Street fails to approve the report before parliament is dissolved on Tuesday, it will not be possible to publish it before the election on 12 December, even though Grieve told MPs it “comments directly on what has been seen as a perceived threat to our democratic processes”.

It is understood that the dossier examines allegations that Russian money has flowed into British politics in general and the Conservative party in particular. It also features claims that Russia launched a major influence operation in 2016 in support of Brexit.

One of those targeted by the Russians at the time was Arron Banks, Nigel Farage’s financial backer. The Briton was offered the chance to invest in a gold deal by Russia’s ambassador to the UK but he ultimately declined. Banks has consistently said that he did not take any money from Russia.

The report is understood to have already been cleared by Britain’s intelligence agencies but a Downing Street spokesman said the approval process “usually takes several weeks to complete”. Sources said the process typically lasts six weeks and the document had only been sent over two weeks ago.

Intelligence and security committee sources responded by saying that Downing Street’s claims were not true and that the normal approval timescale was not six weeks but 10 working days. Opposition politicians accused Johnson of staging a political cover-up ahead of the election.

Ben Bradshaw, the Labour MP for Exeter, asked what ministers had to hide by withholding clearance. “People will be justified in drawing the conclusion that the report’s findings are compromising or worse for the government and the Tory party,” he said.

The intelligence and security committee, which meets regularly when parliament is in session, had been working on a report about Russian attempts to infiltrate Britain’s democratic processes for several months. It had hoped to make its recommendations before the election, which has been widely anticipated for some time.

But Grieve, making a point of order in the Commons on Thursday morning, warned that the release of those recommendations may now not take place. “Parliament and the public ought to have, and must have, access to this report in light of the forthcoming election and it’s really unacceptable for the prime minister to sit on it and deny them that information,” Grieve said.

John Bercow, the Speaker, said ministers would have heard the appeal, adding: “I would hope that as the leader of the house [Jacob Rees-Mogg] is sitting on the frontbench, we might make progress on this matter. It can be expedited, potentially, and the leader might be willing to act as a messenger and we’ll have to see what the result is.”

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Bercow said he hoped that it would not be necessary for Grieve to have to raise the matter again.

One of those who gave evidence to the committee was William Browder, a financier and human rights campaigner. His testimony raised concerns about the willingness of former British diplomats, intelligence officers and establishment figures to work on behalf of Russian interests.

Browder’s evidence named Labour attorney general Peter Goldsmith among those who have conducted advisory and lobbying work on behalf of Russians who wanted to avoid being hit by EU economic sanctions.

When reports of its work first emerged, Lord Goldsmith’s law firm, Debevoise & Plimpton, said it could not comment on confidential matters and that everyone is entitled to legal representation.

It emerged at the same time that Goldsmith’s law firm had instructed a firm run by Boris Johnson’s election adviser Lynton Crosby, CTF Corporate & Financial Communications Ltd, to help them research the EU sanctions landscape. At the time, Crosby’s spokesperson said he was working with the British Conservative Party and would not have known what the firm was doing for other clients. CTFCFC said it was not involved in lobbying and simply conducted research on behalf of the law firm.

The intelligence and security committee exists to provide cross-party oversight of the government’s security and intelligence activities. Its reports are cleared by Downing Street to check if there is any information that it believes would be prejudicial to the UK’s national security interests.

Stewart McDonald, the SNP’s defence spokesman, said: “Boris Johnson has now had this report for two weeks and it would be wholly unacceptable for parliament not to be given its contents before being dissolved.”