"The board also regards a price of 260 pence per share as inadequate, having regard to the stand-alone value of EMI, the synergies available from a combination with WMG and the risks identified above."
Warner, the world's fourth-largest music company and with artists including Madonna and the Red Hot Chili Peppers, approached EMI about a possible bid at the end of January despite uncertainty over whether it would win European regulatory approval.
Warner Music declined to comment.
EMI had said it would consider any bid in terms of the price offered and whether it would be approved by European regulators.
The potential offer price is in line with many analysts' expectations but they noted that EMI may be reluctant to engage at that price, amid media speculation that the firm was also in talks with a number of private equity funds.
The Financial Times reported on Feb. 22 EMI was in talks with private equity firms including One Equity Partners, a unit of JPMorgan Chase , as potential alternatives.
EMI and Warner have been in a tit-for-tat takeover battle for seven years and last year Warner offered 320p a share for EMI.
The music industry has struggled in recent years as the growth in legal downloading has not made up for the slide in physical sales, but EMI has been hit particularly hard, with the poor performance of new releases such as Williams's "Rudebox".
Shares in EMI, which issued its second profit warning in as many months in February, rose by as much as 8 percent after it rejected the proposal. The shares closed 4.45% higher at 246-1/4 pence.