Sky said IHG's board met a few weeks ago to consider the offer, but turned it down on the grounds it was too low.
A spokeswoman for IHG, which runs 4,700 hotels with brands such as Crowne Plaza, Holiday Inn and Intercontinental, declined to comment on the report.
Sky said the identity of the bidder was unclear, but cited analysts as saying it might have been Starwood Hotels & Resorts or a specialist investment fund such as Starwood Capital.
Sky said IHG was braced for the bidder to return with a new offer, or for a rival suitor to come forward.
($1 = 0.5938 British Pounds) (Reporting by Li-mei Hoang; Editing by Mark Potter)