The development was announced by the Takeover Panel, which presides over City rules governing bids for UK firms, as the clock ticks down to its deadline for American suitors 21st Century Fox and Comcast (Swiss: CMCSA.SW - news) to make final offers for the UK-based home and mobile entertainment and communications company.
The panel's ruling sets the scene for an auction that begins at 5pm on Friday and ends the next evening, as all sides involved in the process agreed to waive usual procedure for a contest over five days from Monday - the first working day after the deadline.
Comcast is currently leading the bids for Sky in financial terms, offering £14.75 per share last month.
That values Sky at almost £26bn.
Fox was yet to raise its £14 per share bid for the 61% of Sky that it does not already own.