The battle for Equity Office Properties Trust has intensified with a rival bidder stepping in to trump The Blackstone Group's $36bn (€27.8bn) bid by 7%.

Vornado Realty Trust, a US-listed property company with a market capitalisation of more than $34bn, has joined with two private US real estate firms, Starwood Capital and Walton Street, to offer $52 a share in cash and stock for Equity Office.