IOF said in a statement that its board has assessed Oxford's binding proposal and determined it to be superior to the Blackstone offer.

IOF said Blackstone has until Oct. 18 to match or outbid Oxford's offer. A Blackstone spokeswoman declined to comment.

IOF last month postponed a shareholder meeting to vote on Blackstone's offer, choosing instead to engage with Oxford after the Canadian company sweetened its bid.

Oxford upped its offer for IOF to A$5.60 a share, which was A$0.10 higher than Blackstone's latest bid and valued Investa at A$3.35 billion (1.8 billion pounds).

Blackstone initially bid A$3.08 billion for Investa in May.

(Reporting by Aby Jose Koilparambil; editing by Richard Pullin)

Stocks treated in this article : Blackstone Group LP, Investa Office Fund