Telephone sex has come to Japan, and it has gray-suited executives of the world's biggest corporation squirming - with embarrassment.

Scores of "phone-a-moan" lines have taken over more than one-fourth of the business of Dial Q2, an 18-month-old information-call service that at first provided sports results, advertisements and medical guidance.Going beyond the lead of tele-porn pioneers in the United States, Japan's entrepreneurs buy space in tabloid newspapers, sports dailies and mass-circulation magazines to run full-color photos of seminude women as promotions for tape-recorded sex programs or a purported chance to talk with a female porn star.

For NTT, the national telephone company and the world's biggest corporation, the influx of pornographic telephone offerings has created a headache that, company officials say, far outweighs the revenue they bring in.

The company acknowledges that a spate of complaints has come in, especially from parents of teenagers. Some of the parents said they found out about the pornographic lines only when their phone bills began to include hundreds of dollars a month in calls run up by their children.

The complaints have forced NTT to search for legal grounds to unplug the porn lines, to offer extended monthly terms to customers who find their phone bills suddenly out of control and to provide a free service that blocks access to Dial Q2 at the customer's request.

They also have prompted a flood of newspaper and magazine editorials demanding an end to the pornographic telephone schemes.

Most have made a point of mentioning that, while NTT was legally privatized in 1986, the company has not yet managed to sell most of its stock and is still owned mainly by the government.

Some articles have portrayed the telephone-sex lines as the product of attempts by Hisashi Shinto, the veteran executive brought in to guide NTT's transition from public to private, to shake up the mind-set he inherited from the government and inject some life into a stuffy bureaucracy that was about to face competition for the first time in its history.

Nihon Keizai Shimbun, the newspaper of Japan's corporate power elite, reported that Shinto brought lingerie advertising to one board meeting and told the company's directors that they should, "have the courage to sell even women's underwear" by telephone.

"The daring of Dial Q2 was born of Mr. Shinto's spirit," the article said.

Shinto resigned in March 1989 after being arrested and charged with bribery in the stock-for-favors scandal that rocked Japanese politics that year.