The consortium's bid values the bookie at more than £3.6bn, the Financial Times reported.
At the end of July 888 and Rank confirmed they were launching a takeover offer for the only major UK bookmaker that has yet to consolidate, despite a wave of mergers and acquisitions that have swept the gambling industry.
“The consortium sees significant industrial logic in the combination, through consolidation of their complementary online and land-based operations,” said a joint statement by Rank and 888.
In a cold response, William hill said it would "listen to and consider any proposal which might be forthcoming from the consortium".
However, it added: "It is not clear that a combination of William Hill with 888 and Rank will enhance William Hill's strategic positioning or deliver superior value to William Hill's strategy which is focused on increasing the group's diversification by growing its digital and international businesses."