However, Taubman Centers stock soared 8% Wednesday morning to $16 per share. The offer still represents a record price for Taubman Centers shares, Simon Property Group officials note.

"Our offer represents a compelling strategic and financial transaction that would produce substantial and immediate value for all of your shareholders," says chief executive officer David Simon in a letter to Taubman Centers directors. "We can move quickly since our offer is not subject to the receipt of financing or any due diligence investigation of the company."

Simon wrote directly to directors, saying at least two previous attempts to make an offer were rejected by Robert S. Taubman, chairman, president and chief executive officer of the high-end mall owner and developer.

"While it is entirely appropriate for the Taubman family to retain the right to choose between various options with respect to the treatment of its own partnership units, it is improper for these insiders to prevent public shareholders from choosing to receive a premium for their shares," Simon says in his letter to Taubman directors.

Taubman officials were not immediately available for comment on Simon's complaint that its offers were not getting a fair hearing.

While Simon Property Group owns 185.8 million sf of retail space in 249 properties, Taumban Centers owns 22 million sf of space, but it developing six more projects nationwide that will add more than 6 million sf to the total.