"Let me be clear: half measures are not acceptable," he told an audience of food and beverage representatives, nutrition experts, consumer groups and advertising specialists at a Federal Trade Commission workshop on obesity and marketing in Washington DC.
"The hour is too late. Children are at risk. The time to act is now."
Harkin, the ranking Democrat on the Senate subcommittee that funds health initiatives, said that food advertising targeted at children was fast becoming the critical issue. An independent, rigorous system of self-regulation for food advertising to children was vital.
"If you move ahead boldly with such a system, I will applaud you, parents will applaud you, and the American public will applaud you," he said. "But if you fail to do so, you will have missed a tremendous opportunity.
"The result, I predict, will be a public backlash."
The stakes are huge. According to the National Health and Nutrition Examination Survey (NHANES), over the past three decades, rates of obesity have tripled for children ages six to 11 years and more than doubled for children ages two to five years and adolescents 12 to 19 years.
The 1999 - 2002 NHANES estimated that 16 percent of children and adolescents ages six to 19 years are overweight.
And food companies are increasingly in the firing line. Lawyers are increasingly targeting the manner in which some firms advertise their products, claiming they breach fraud statutes by misleading consumers into thinking that certain products are healthy and nutritious when they are not.
The food industry has of course taken notice. Harkin applauded the GMA (Grocery Manufacturers of America)'s idea to limit product placements in TV shows, and the use of licensed characters in ads and food packaging. But he warned that a stringent self-regulation mechanism must be put in place.
"I have not seen details of the GMA proposals, so I will withhold any final judgment. But based on what I have read so far, there appears to be no meaningful enforcement mechanism . . . no truly independent body with the will and the power to crack down on offenders."
Harkin says that any meaningful system of self-regulation must include parents, public-health experts and child development experts, and must be independently monitored. "And it needs an independent oversight body with teeth - with the power to punish bad actors that violate the agreed-to standards."
He also attacked food industry lobby groups that claim there is no evidence that food marketing is responsible for kids eating junk food and consuming more calories.
"Corporate America doesn't spend $12 billion a year on advertising aimed at children because it likes to waste money," he pointed out. "Corporate America spends $12 billion because that advertising works brilliantly. . . . because it persuades children to demand a regular diet of candy, cookies, sugary cereal, sodas, and all manner of junk food."
Critics remain angry that little has been done so far to curb the aggressive marketing of junk food. Last month for example, the Connecticut governor's decision to veto a nutrition bill that would have outlawed soft drinks and junk food in schools, was met with astonishment and incredulity.
"We are extremely disappointed that Governor Jodi Rell vetoed the school nutrition bill," said CSPI (Center for Science in the Public Interest) nutrition policy director Margo G. Wootan.
But Harkin believes that public pressure for change is building.
"According to Yale University polling, in 2001, 57 percent of Americans favored restricting children's food advertising," he said. "In 2004, 73 percent of Americans favored such restrictions. The backlash is building steam."