The war of words ramps up over the release of the dossier into Kremlin meddling, amid claims the PM is sitting on the report.
Downing Street has been accused of telling «whopping untruths» over the publication of a report into the threat posed by Russia to the UK’s democratic processes.
The claim by former attorney general Dominic Grieve ramps up the war of words with Number 10 over the release of the dossier, which he argues is essential ahead of the election.
Labour leader Jeremy Corbyn has also demanded its publication, questioning what the government «has got to hide».
Mr Grieve, the chair of parliament’s Intelligence and Security Committee (ISC), alleges the prime minister is sitting on the report ahead of the 12 December poll.
The independent MP, who was kicked out of the Tories by Boris Johnson over his opposition to no-deal Brexit, is calling on the Conservative leader to publish the committee’s report before parliament is dissolved on Tuesday.
The House of Commons has previously been told the report was sent to the PM on 17 October.
Mr Grieve says Downing Street should have signed off the report within 10 working days, but No 10 disputes this and maintains the process usually takes six weeks.
Parliament is expected to sit on Monday and Tuesday ahead of dissolution although proceedings could be brought to an end sooner, which may prevent the report’s release.
Speaking to Sky News, Mr Grieve said: «If it can’t be published by Tuesday it will not be published at the earliest until April or May of next year.
«It does have a bearing on electoral processes because we know that the Russians have in other countries interfered in their electoral processes.»
He said that Downing Street’s six-week claim on clearing the report was «completely and totally untrue».
Mr Grieve added: «It’s a lie. I really get worried about this. The process of getting this report cleared is finished.
«The last stage — the clearance by the prime minister — is programmed for 10 days.
«The suggestion that six weeks are needed is just astonishing.
«They are coming out with things that are quite simply whopping untruths and they must know it.»
He added: «I find it really worrying. What on earth is going on when people can come along and authoritatively suggest something which is complete fiction.
«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 please.
«It would be exceptional. It has never, ever happened before.»
The Remain-supporting MP dismissed any suggestion that his call was linked to continuing tensions over the referendum.
Former Tory chair of the intelligence and security committee Sir Malcolm Rifkind has told Sky News that he can see «no reason that has been given» by Downing Street to explain why the release of the Russia report should take longer than a few days.
Sir Malcolm said delays are usually caused by national security issues, but that should not apply in this case because the report has already been vetted by intelligence agencies.
The former foreign secretary also said it was «disturbing» that if the report was not published before the election, it would likely be delayed for several months while the Committee is re-formed and its members security checked.
He said if Downing Street have a valid reason for not clearing the report, the prime minister should explain them to Dominic Grieve on a confidential basis.
Meanwhile, Mr Corbyn told reporters: «Yes it should be released.
«And I suspect that the reason it hasn’t been published is because they’re going to delay it past the dissolution of parliament on Tuesday and then they can hide it away until some point in the future.
«If a report has been called for and written, and it should be in the public domain, then what have they got to hide?»
Sky News understands Christopher Steele, the former head of MI6’s Russia desk, gave evidence to the ISC inquiry.