KANSAS CITY, MO. — When the mayor named a 73-year-old grandmother to the city’s park board — which considers issues like off-leash dog areas and outdoor party permits — the move might have gone largely unnoticed.

But Frances Semler’s appointment could now cost the city millions of dollars because she is a member of the Minutemen, a group that advocates vigilante patrolling of the Mexican border and reports illegal immigrants to authorities.

Her membership has drawn sharp criticism from the National Council of La Raza, the nation’s largest Hispanic advocacy group, and the NAACP. Both groups are threatening to show their displeasure by canceling conventions scheduled to be held in Kansas City.

“We see the Minutemen as an extremist group that espouses hate and vigilanteism and some violence,” Janet Murguia, president of NCLR, said. “A member of such a group, no matter how upstanding in other ways, should have no place representing Kansas City.” The NCLR’s four-day convention in 2009 is expected to generate $5.5 million in revenue for hotels, restaurants, and other businesses. The week-long conference by the National Association for the Advancement of Colored People in 2010 could bring in $9 million. Ms. Semler, who said she will not resign, calls the threats from the civil rights groups “the most ridiculous thing I’ve ever heard.” She said she joined the Minutemen because of the government’s failure to enforce immigration laws.

Minutemen members “sit on lawn chairs with binoculars and a can of Coke or something and watch to see if anyone is coming across” the border, Ms. Semler said. “I’m not even sure if they’re armed, but there might be cases if a person has a legal right to carry a gun.”

When Ms. Semler’s appointment first drew attention, Mayor Mark Funkhouser turned down her offer to resign. He then said he would continue to support her, even if it meant losing the two conventions and any other events.

“I am a member of the NAACP, and I’ve been a longtime supporter of civil rights and diversity,” Mr. Funkhouser said in an e-mail to the Associated Press.

The five-member parks board that includes Ms. Semler also has two black members and a Hispanic president. The mayor has said he appointed Ms. Semler, a neighborhood leader, because he thought she “would work hard to make our parks a better place for children.”

“I don’t share Ms. Semler’s views regarding diversity, but if I’m going to champion diversity, I’ve got to defend diversity of opinion and political thinking along with ethnicity,” he said.

Ms. Semler has said she supports legal immigration, but wants to halt it until immigrants waiting to become American citizens are processed.

“I’m not a racist,” she said. “Legal immigration is what makes this country great. If you feel like maybe you don’t love this country enough, go talk to some immigrants.”

She said she does not attend many Minutemen meetings because she is too busy dealing with parks-board matters, serving as president of the Clay County Rose Society and helping her husband with his home-remodeling business.

The mayor said he welcomed talks with the NCLR and the NAACP on their convention plans and on Ms. Semler’s appointment. The La Raza board and the NAACP both plan to decide in October whether to cancel their conference plans in Kansas City.

The city could also gain a convention because of Ms. Semler.

On Friday, the Kansas director of the Minutemen announced the group would hold a two-day national convention there in early December. That meeting was expected to attract about 300 people.