Brexit’s biggest funder, Arron Banks, met the Russian ambassador at least 11 times in the run-up to the EU referendum and in the two months beyond, documents seen by the Observer suggest – seven more times than he has admitted.

The same documents suggest the Russian embassy extended a further four invitations but it is not known if they were accepted, according to the Guardian.

It is the third time the number of such meetings has been revised upwards. For two years, Banks insisted his only contacts with the Russian government consisted of one “boozy lunch” with the ambassador.

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After the Observer revealed a month ago that he had multiple meetings at which he had been offered lucrative business deals, Banks told a parliamentary inquiry into fake news he had had “two or three” meetings.

Read alsoArron Banks 'met Russian officials multiple times before Brexit vote' – media

Last week, when pressed by the New York Times, he admitted a fourth meeting. But the Observer has seen evidence that suggests there were at least seven more. When questioned about this, Banks offered no response.

The Observer has seen details, and the Sunday Times published an email given to it by Banks, suggesting possible deals were presented at the fourth of these meetings, on 17 November 2015, the same day that the Leave.EU group – which he helped fund – officially launched its campaign.

The document suggests Banks messaged Siman Povarenkin, the oligarch introduced to him by the ambassador, saying: “I’ve chatted to Jim Mellon who is my partner in the bank and we are both interested in looking at how we could help. Jim has extensive interests in commodities.” Banks goes on to say that another business partner will be in touch “to start discussions. I’m very bullish on gold so keen to have a look”. As a postscript, he adds that “Jim knows the ambassador as well!”

Mellon is an Isle of Man-based investor who made his estimated £850m fortune in Russia in the early 1990s.