Not Ready for Prime Time? The Democratic National Committee yesterday filed a complaint with the Federal Communications Commission against CBS Inc. for broadcasting President Reagan's speech on the economy Wednesday night and failing to give the Democrats a fair chance to respond.

The complaint said the president's address, coming less than three weeks before the midterm elections, was "blatantly partisan" and it thus obligated the networks, under the FCC's Zapple Doctrine, to provide equal opportunity for supporters of Democratic candidates to respond.

It noted that ABC chose not to air the president's speech, and NBC offered the Democrats a choice of a live six-minute response immediately after the presidential address or a 30-minute response in the same time slot the following day. The party chose to put Sen. Donald W. Riegle Jr. (D-Mich.) on NBC live after Reagan spoke.

But CBS, the complaint said, made no such offers. It aired the "Democratic response" at 11:30 p.m. the same night, and the response came from individuals selected by CBS from around the country to represent the Democratic viewpoint.

The complaint accused the network of "insulting" the American people by relegating a contrasting view to "the deepest recesses of its schedule." It also said that during the height of an election campaign the discretion over selecting spokesmen for a party should rest with the party, not the networks.

The complaints ask the commission to order CBS to broadcast a prime-time Democratic response before Election Day.