ACTRESS LINDA KELSEY of the "Lou Grant" show sat folded up on a brown sofa in a small, upstairs room on Lamont Street yesterday morning talking about the intense suffering of infants she had seen in India, Bangladesh, Malaysia, Hong Kong and the Philippines during a two-week trip in April. She calls these infants bottle babies, because they have been fed with bottled formula instead of breast milk. She talks of bacteria, contaminated water, the heat and the flies that ruin the formula and of poverty so pervasive that a family that spends 85 percent of its monthly income on infant formula can't throw it out even if it has spoiled in the sun.

She takes out a poster the size of a piece of typing paper. There are four simple pictures of baby bottles with the skull and crossbones etched across them. Written in Bengali on the poster is the slogan "mother's milk is the best food for babies." The literacy rate in Bangladesh, she says, is 20 percent, so maybe some mothers will get the messages. But many haven't and many won't. That poster, distributed by doctors at clinics, can't do much to offset the marketing and advertising of the $2-billion infant formula industry.

"It's given a kind of glamor," says Kelsey, "that makes women think it would be better." Formula advertisements show pictures of "a lovely, fat baby, usually a Western baby, and the implication is your baby will look like this. Third World babies are very, very small. When a milk nurse comes into the hospital who works for a formula company with her free samples to give the baby a bath, it looks like it has the endorsement of the medical profession."

Kelsey and her husband, Glenn Strand, who went with her on the trip which was sponsored by the International League of Consumers Unions, met a family of 13 in Bangladesh with a 12-day-old baby. "They said they were going to start formula feeding," says Kelsey, even though they had an income of $34 a month and lived in a tiny hut. "A few yards away were tiny shops (in corners of other family homes) with the most incredible displays of infant formula."

"There is such a great desire to emulate the West," says Strand. The mother who bottle feeds, instead of breastfeeds, gains status. She is a modern mother.

Experts have estimated that as many as 1 million Third World babies die each year as a result of diarrhea; and malnourishment associated with misused and contaminated formulas. The World Health Organization's assembly in Geneva voted overwhelmingly Thursday to adopt a strict code to enforce ethical marketing practices on the infant formula manufacturers. The United States, once a strong supporter of such a code, cast one of three votes against it. Despite the fact that the code is recommendatory and not mandatory, the Reagan administration raised antitrust and First Amendment objections to it and said there is no proven relationship between the marketing of formula and infant health.

Up until the end, a bipartisan congressional delegation made extraordinary efforts to get to a once-approachable president to tell him that the code involved not just free enterprise and regulation of business but the lives of babies. They were repeatedly rebuffed by the White House. Rep. Thomas Harkin (D-Iowa) says he first tried to get an appointment for the delegation through congressional liaison Max Friedersdorf and found he had to brief him on the issue. When Friedersdorf didn't call back, Harkin again called for an appointment and was told finally told by William J. Gribbin of the liaison office that there was no time on Reagan's schedule.

"I called him back and said, 'Look, who said we couldn't get on the president's schedule? Did the president say that?' He said he didn't know," but that the decision came through the offices of presidential counselor Edward Meese and White House chief of staff James Baker and a call to them would simply be referred back to Gribbin. "I said, 'Let me tell you, Mr. Gribbin, what my feelings are and perhaps you can pass it on.' I said, 'I cannot believe the president can't find 10 minutes in the day to meet with 12 to 15 members of Congress on an issue of this importance. I know how tight a president's schedule is, but I also know that you can squeeze, that you can push a calendar a little bit. . . I don't want to see the president to give him a 10-gallon hat or to declare June 15 National Tulip Day. This is something much more important.'"

Harkin believes the administration decision to vote no was made at the political level at the White House and that White House advisers then wanted to prevent people from getting to Reagan who could appeal to his "better sensibilities."

Just how busy the president could have been this week is a good question. He found time to go to the ballet and to yet another of the private dinners with his Hollywood cronies. He has rarely worked in the afternoon since the shooting, although he is well enough that on Wednesday he received permission from his doctor to resume wood chopping and horseback riding, which he will do during this long weekend in California.

But when a bipartisan delegation of congressmen wanted to talk about Third World babies dying, Reagan didn't have time. Linda Kelsey said she was appalled by what she found on her trip to the Third World, and she came to Washington to try to stop it.

What she found here, she said, was frightening.