New York Governor Eliot Spitzer, a former state attorney general who prosecuted some of the biggest firms in the United States, said on Tuesday that recent options trading ahead of takeovers was "deeply problematic."

In past months, announcements of proposed buyouts such as a $32 billion takeover of utility TXU Corp. (TXU.N: Quote, Profile, Research, Microsoft Corp.'s (MSFT.O: Quote, Profile, Research purchase of aQuantive Inc. (AQNT.O: Quote, Profile, Research and Rupert Murdoch's $5 billion offer for Dow Jones & Co. Inc. (DJ.N: Quote, Profile, Research, have been preceded by unusual spikes in options trading, raising questions about whether the news was leaked.

"Some smart prosecutor somewhere is going to be dropping a lot of subpoenas wanting to know who placed all these options purchased in the 48 to 72 hours before the deals were announced," Spitzer predicted in an interview on CNBC.

"There are a lot of people who should be very nervous about that," he said.

Authorities are already looking into some of these deals. Earlier in May, federal prosecutors in New York brought charges against a junior-level investment banker at Credit Suisse Group (CSGN.VX: Quote, Profile, Research, charging he divulged inside information on TXU and other yet-to-be-announced merger deals to a banker in Pakistan.

Also in May, the U.S. Securities and Exchange Commission filed a civil suit against a husband and wife in Hong Kong over trading in Dow Jones shares.

Options contracts give investors the ability to bet on a steep rise or decline in a stock price without having to put up the money to buy the actual shares.

As attorney general of New York, Spitzer made a name for himself by filing charges against famous individuals such as former American International Group Inc. (AIG.N: Quote, Profile, Research Chief Executive Maurice Greenberg.

He won a $10 billion settlement from the largest U.S. investment banks for biased research.