The Securities and Exchange Commission today filed suit here charging a Spanish securities firm and its New York subsidiary with bilking several major brokerage houses by selling and not delivering U.S. and European stocks and bonds.

SEC officials said the securities involved are worth at least $230 million. Transactions cited in the suit, all made within the past two months, involve at least six Wall Street brokerage firms, which now face losses of at least $21 million stemming from the Spanish firm's actions.

The six firms are Merrill Lynch, Pierce, Fenner & Smith Inc., which sources said is exposed to about $8 million in losses; Advest Group Inc., which said Monday that it faces a quarterly write-off of $1.5 million for unnamed securities that had not been delivered by a customer; Bear Stearns & Co., which faces an exposure of less than $2 million; Lehman Brothers Kuhn Loeb; Ernst & Co.; and New York and Foreign Securities Corp.

The suit names as defendants the Madrid firm, C.&R. Pastor Securities Ltd., S.A.; its wholly owned New York subsidiary, C.&R. Pastor Inc.; the president of the New York firm, Raphael Pastor; and its vice president, James Anthony Lockhart. No defendants could be reached for comment.