For more than 20 years, McDonald's has operated a popular fast-food outlet inside Abbott Northwestern Hospital in Minneapolis.

Now a Boston-based advocacy group is asking the hospital to give McDonald's the boot.

Last week, the group -- Corporate Accountability International -- sent letters to Abbott and 21 other U.S. hospitals with McDonald's franchises, urging them to "stop fostering a food environment that promotes harm, not health."

Sara Deon, the project director, argues that fast food is one reason so many kids are obese. So it's indefensible, in her view, for hospitals to give aid and comfort to the biggest fast-food company of all. "It really runs counter to the goals of a health institution," she said.

Abbott has been a little sheepish about the subject ever since its McDonald's opened in 1990. At the time, news stories boasted that the company had agreed to modify its menu at the site, adding apples, skim milk and vegetable soup, to ease the hospital's concerns.

Abbott officials declined to answer questions about the new campaign, but they released a written statement this week: "McDonald's was the only vendor that was willing to negotiate a menu with healthier options," it said. Today, it also offers salads, yogurt, oatmeal and fruit alongside the Happy Meals and Big Macs.

"We understand that some people are concerned about the presence of McDonald's on a hospital campus," the hospital said. But the contract is "long term, with an expensive buy-out option," it said, and "we do not believe that buying out the contract would be worth the expense."

McDonald's, meanwhile, issued a statement saying it is "proud of our menu" and that "it's not about where you eat; rather, it's about what and how much."

Deon admits that the campaign is largely symbolic, what with all the fast-food outlets in the country. "We are really just urging hospitals to continue their leadership role," she said. "We see it as the beginning of a conversation."

Maura Lerner • 612-673-7384