Last month, the Spanish stock-market regulator approved Grupo Inmocaral's takeover offer for the much larger office property group Inmobiliaria Colonial SA. The merged company has a market capitalization of about $8.8 billion.

But, as Rivero indicated, his interest in bidding for Colonial was impossible given the bidding war that has broken out over control of Metrovacesa. An investment vehicle set up by Rivero and Soler has an approved 80-euro-per-share bid for 26% of Metrovacesa on the table, but this was topped on Monday by an improved 90-euro-per-share bid from fellow board member Roman Sanahuja Pons.

The Sanahuja family's new bid is expected to be ruled on by the stock-market regulator in September. The problem for the Sanahuja bid is that a successful bid would take their shareholding in Metrovacesa to over 50% and trigger an automatic full bid for the company. But they have given no indication as to whether they would be prepared to launch a full bid or how they would fund it.