A leading cable television industry spokesman today downplayed the importance of increasing uncertainty about the future of cable programming and urged the National Cable Television Association to join a nationwide public relations campaign to sell cable's services.

The remarks were contained in the text of a speech that NCTA President Thomas E. Wheeler was scheduled to make here Monday as the NCTA opened its 32nd annual convention.

In addition to touting a newly formed industry marketing effort, Wheeler lashed out at a familiar cable industry adversary, American Telephone & Telegraph Co.

He called an AT&T campaign to block Senate cable deregulation legislation "deceptive." AT&T officials--in what is likely to be the last major Bell System political effort before the company's breakup--have said deregulation of cable data-transmission services threatens phone company revenues and could force further local phone-rate increases.

Such data services offered by telephone companies are now regulated and the bill, due for a Senate vote on Tuesday, would virtually deregulate the whole spectrum of cable data transmission services.

The bill, which if enacted would be the government's most sweeping cable law, was adopted by the Senate Commerce Committee by a 15-to-2 vote in April. It was scheduled for Senate floor action a month ago but sponsors sought a delay after opponents threatened a filibuster.

The measure is opposed by some major city leaders, including New York Mayor Edward Koch, although it has been endorsed by the National League of Cities. The bill sets a limit on the franchise fees municipalities can charge cable systems and establishes the first nationwide franchise renewal guidelines.

The legislative fight comes at a significant time during cable's development. Cable systems now serve about 30 million subscribers, or about 38 percent of all television households.

But advertiser-supported cable TV programming efforts are having major financial difficulties and pay television services have been struggling to challenge Home Box Office's dominance of the industry. A further blow to that challenge came Friday when the Justice Department said it would sue on antitrust grounds to block the merger of HBO's two leading competitors--Showtime and Movie Channel.

Moreover, the cost of cable-system construction is escalating at a time when the industry is pushing to wire the nation's major cities. But Wheeler said any "shakeout" in the cable business "is more figment than reality" and urged executives here to upgrade programs designed to explain cable television services to the public.

Citing an industry-commissioned public opinion survey to be released here Tuesday, Wheeler suggested that the public often lumps together cable and network television, although viewers are increasingly dissatisfied with network fare.

"Potential subscribers are confused or misinformed about the quantity, quality and availability of cable," Wheeler said.

As a result, a group of cable executives has formed the Consortium for Cable Information, Wheeler said. The new group will "mount a national advertising and public relations campaign" and provide local cable operators with materials to allow them to do the same, he said. The organization's chairman is Daniel L. Ritchie, chairman and chief executive of Group W Broadcasting and Cable.