STUTTGART, Germany (AP) - Porsche has rejected Volkswagen AG's bid to take a 49 percent stake in the sports carmaker, a company spokesman said Monday.

Porsche Automobil Holding SE spokesman Albrecht Bamler said the offer by VW "is not a viable option."

According to Bamler, Porsche board chairman Wolfgang Porsche received the offer in a letter by courier last week. But the company's CEO Wendelin Wiedeking and management board were not informed.

"Without the management board, nothing goes here," Bamler said.

Porsche holds a roughly 51 percent stake in Volkswagen, but ran up hefty debts in accumulating that holding and is now seeking a merger with the larger company. Exactly how that is to happen remains unclear.

German weekly Der Spiegel reported the VW offer was worth euro3-4 billion ($4.2-$5.6 billion), which would have helped Porsche pay off it debts, racked up in its attempt to take over VW.

Bamler said, however, that for VW to take a stake in Porsche, the Wolfsburg-based automaker would have to take out credit worth euro10.75 billion ($15.15 billion).

Porsche, based in Stuttgart, confirmed earlier this month it has been holding talks with a Qatar state investment fund, the Qatar Investment Authority, on a possible investment.

Volkswagen shares dropped 10.58 percent on the news to euro237.91 in afternoon trading in Frankfurt.

Porsche shares nudged up nearly half a percent to euro45.92 in Frankfurt.