The Sunday Mirror states that Leeds blundered by putting tickets for the game on open sale.
Fans were allowed to buy up to eight tickets with no questions asked.
That was after Leeds had cut United's official allocation to just 1,600 because of fears of crowd trouble.
Leeds gave official club members the option to buy tickets for the game but limited the number sold to one per person.
They then put the rest on open sale and hundreds were immediately snapped up by touts and Man United fans who missed out on the Old Trafford ballot for tickets for the visitors' enclosure.
When Leeds realised their mistake, they stopped selling the tickets on open sale.
The article states a Leeds insider said: "It is well known that tickets for parts of Elland Road reserved for home supporters have got into the hands of United (Manchester) fans."