The Sunday Express has learnt that businessman Arron Banks, the founder of Leave.EU, has issued a dramatic legal challenge to the publication of the report by the Intelligence and Security Committee. His lawyers have demanded that if attempts are made to rake over previous unfounded allegations against Mr Banks then publication should be delayed to give him a chance to respond.
The long-awaited report was drawn up by the committee under the chairmanship of Remain supporting former MP Dominic Grieve.
It follows a series of false accusations against Mr Banks and other prominent Leave supporters that they were Russian agents.
The legal letter to the committee's new chairman Julian Lewis comes ahead of the expected publication of the report on Tuesday.
In it, Mr Banks's lawyer Kingsley Napley points out that there is an ongoing defamation case over the previous publication of many of the accusations. The letter said: "Mr Banks has not received any invitation to give evidence and/or to respond to any allegations which may be advanced against him in the Russia Report.
"Please provide us with immediate notification of any statements made within the Russia Report which refer to Mr Banks.
"Given the subject matter of the Russia Report and the matters which are currently live in litigation in the courts, it would obviously be necessary, fair and just for him to have advance notice if any statements were to be made about him and that he was given a proper opportunity to deal with them prior to publication
"Not least when it is understood journalists have been given an opportunity to cooperate."
It is understood that certain tweets this week referring to the publication of the report have led Mr Banks's legal representatives to believe he may be mentioned within it.
A source close to the committee has suggested the legal letter may have an impact on delaying the report's publication.
Brexiteer Conservative MP Andrew Bridgen said that he was concerned the Intelligence and Security Committee report will be another attempt to "sabotage" Brexit.
He said: "I hope that the ISC report will not be used as yet another attempt to try to discredit the referendum vote for Brexit or to smear Arron Banks again. Too often we have seen that Remainers cannot accept defeat and have repeatedly used any means possible to attempt to undermine and discredit the result.
"Yet whenever the British people have been asked to vote in a referendum or election in the last four years they have consistently and increasingly overwhelmingly backed the Leave side."
The row over using allegations of Russian influence as part of a "witch hunt" against Brexiteers has already seen two Parliamentary inquiries open into whether the Electoral Commission is "fit for purpose".
This week legal representatives of Mr Banks and his associate Andy Wigmore sent a 25-page submission to the Speaker's Committee inquiry into the Electoral Commission.