Realia is 62 percent owned by builder FCC and bailed-out lender Bankia and is one of the few Spanish property groups to have survived the economic slump following the 2008 housing market crash.

Hispania's offer of 0.49 euros a share values Realia at 150.6 million euros ($187 million) compared with its market value of just over 209 million euros at the close on Friday.

The offer is subject to the acceptance by at least 55 percent of Realia shareholders and includes debts of over a billion euros, Hispania said in statement to the market regulator.

The investment company will spend between 393 million and 470 million euros for a stake of 50.1 percent to 58.2 percent in the real estate firm following an 800-million-euro capital hike at Realia aimed at recapitalising the indebted group.

Hispania also called an extraordinary shareholder meeting for the end of December to approve a 44.3-million-euro capital hike of its own.

Realia's net debt stood at 1.1 billion euros at end-September, more than five times its current market value, and owns offices and shopping centres across Spain, including one of Madrid's landmark leaning towers in Plaza Castilla.

FCC is selling non-core assets to cut its debt while Bankia must divest corporate holdings as a condition of a 2012 state rescue backed by European funds.

(1 US dollar = 0.8072 euro)

(Reporting by Jose Elias Rodriguez; Writing by Paul Day; editing by Susan Thomas)