Mr McCluskey received private jet flights to watch the team he supports, Liverpool FC, play in the 2018 and 2019 Champions League finals in Kyiv and Madrid, according to Unite’s report.
Sources have told the BBC that on one occasion he travelled on a Falcon 900B business jet.
The plane’s owners said it offered passengers “super size comfort” including “8 leather club seats, a full size bed, fully stocked galley and cabin sound system”.
Aviation company Global Charter has estimated the return trip would have cost between £40,000 and £47,500.
Unite’s report also claims that Mr McCluskey received tickets for five Liverpool FC games in the UK, four of which included matchday hospitality.
It said “the evidence for this comes from tickets and flight information sent to Len McCluskey’s Unite email”.
Mr McCluskey’s lawyers said he paid for his travel in full and recalled travelling with a commercial carrier on one of the flights.
They said he occasionally attended football matches with the Flanagans but invariably paid his way and does not believe he even attended all of the domestic matches as claimed by Unite’s report.
There is no suggestion Mr McCluskey breached Unite’s gifts or hospitality rules because there was no such policy. Sharon Graham has since introduced a gifts and hospitality policy.
She has also recruited a new finance director and procurement officials as part of what she calls her “clean up” effort.
“Maybe it took a woman to do it”, she said. “And now I’ve uncovered it, I’m going to make sure that it never happens again.”
Ms Graham is also attempting to get back some of the millions spent on the hotel. “Because this is members’ money, I expect it back in the union”, she said. “And I’m going to do everything in my power to make sure that happens.”