The D.C. Cable Design Commission, halfway through its 90-day effort to devise a proposal to regulate how cable television should operate in the District, says it needs more time and has voted to ask the City Council to approve up to a six-month extension.

The 28-member commission, which voted 14 to 11 last week to ask for the delay, said it does not have enough time to complete committee work on such issues as cable ownership and other technical aspects of the industry to meet the April deadline.

Because the city is late getting into the cable business, the commission also is exploring the effects of other technological developments such as direct broadcast satellites that could make cable business less attractive in the District.

If the council approves the delay, it probably could not award any cable franchises until at least mid-1984, according to City Council member Betty Ann Kane (D-At Large). Actual cable service in the District, which trails far behind other jurisdictions, is still thought to be a couple of years away.

Kane, chairman of the council's cable committee, said yesterday that she preferred a commission extension of no more than 60 days. She said that if the commission delayed its report, it would not get to the council until after the council's 1 1/2-month summer recess begins July 15.

"We need a couple of months at the council," Kane said. She said her committee would have to hold public hearings on the cable commission's work and that she expected the council to make changes in whatever the commission recommends. The council voted itself the right to award cable franchises.

The formal "request for proposals" that the commission writes will be used as a guide by cable companies that want to win the potentially lucrative rights to set up cable systems in the District.

Commission chairman William Lightfoot, who opposed the vote for a delay, said yesterday that he believed the extra time would disrupt the commission's schedule and unnecessarily put off the ultimate award of a cable franchise.