The company had already to sell its radio stations in the Republic of Ireland to Communicorp Group for €200 million (US$275.8 million) in cash.
Emap said in a statement that because of its announcement an offer period had begun.
Still, "the board confirms it has not received any approach to acquire Emap as currently constituted and that the commencement of the offer period is not a consequence of any proposal received to date."
Analysts have been critical of Emap's management in recent years as the company has tried to find new growth revenues amid a weak advertising market.
Emap shares gained 1.4 percent to 848.5 pence (US$17.85; €12.18) on the London Stock Exchange.