"The Electoral Commission has laid out concerns about this in public and it is legitimate and editorially justified for Andrew Marr to question Mr Banks robustly about them, which he will do on Sunday morning".
Mr Banks told the BBC's Andrew Marr the money came from his United Kingdom businesses.
Mr Banks's funding of the Brexit campaign is the biggest donation in British political history.
The founder of Leave.EU is the subject of a National Crime Agency (NCA) probe into the source of payments.
The Electoral Commission says it suspects the money came from Rock Holdings, the parent company of Rock Services, which is registered in the Isle of Man and so "could not lawfully make any donation or be a party to any loan to Leave.EU".
But Mr Banks told Marr that it came from a UK-based insurance business, saying: "There was no Russian money and no interference of any type".
"For Rock Services to have money to give to Leave.EU or anyone else, that money has got to have been put in that bank account by another company or another individual".
Mr Banks has been accused of misleading Parliament over links between Leave.EU and his insurance businesses.
"Contrary to some of the press reports in the Financial Times and other Remain-leaning publications, we insure almost half a million customers a year - the size of Manchester".
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BBC correspondent John Simpson defended the decision, writing: "The urge to keep people we disapprove of from appearing on our TV screens is very much the same as the desire some university students have to no-platform speakers whose views they disagree with". "It's a sizeable business".
In the BBC interview on Sunday, Banks was also asked about a report in the Sunday Times that he would back the Remain campaign in a re-run of the 2016 referendum.
Mr Banks revealed he had seconded a small number of people to run a call centre in Bristol but stressed this was properly declared to the Electoral Commission.
"If Rock Services made the donation, where did the money come from for Rock Services to do that?"
"It's a group of vicious MPs who have grouped together with the Guardian and the FT".
The Electoral Commission is not responding to Mr Banks' comments. Asked why he had written to Mr Collins's constituents in Folkestone and Hythe, calling him a "snake in the grass", Mr Banks replied: "Well, he is".
Both Bilney and Banks deny any wrongdoing, with the latter posting a flurry of tweets on Friday evening.
Banks also stated he was confident the NCA would clear him and his campaign, branding the Electoral Commission a "shambles" and dismissing the whole exercise an attempt by the Remain campaign to "tarnish" the Leave campaign and derail Brexit.