Kirsten Kukowski, a spokeswoman for Mr. Kirk’s Senate campaign, did not respond on Friday to the comments from church officials. In a statement earlier in the week, she said Mr. Kirk had worked “as a nursery school teacher” in his final year at Cornell. Campaign officials began an inquiry into the scope of Mr. Kirk’s work after receiving questions from The Times.

“Congressman Kirk believes his time working in a nursery school and middle school provided valuable life experience,” Ms. Kukowski said Friday in a statement.

The Kirk campaign has scrambled this week to try to confirm details of his time as a nursery school teacher, which he raised as recently as March in a speech to the Illinois Education Association. “As a former nursery school and middle school teacher,” he said then, “I know some of what it takes to bring order to class.”

In an interview Friday, Ms. Grubb said that she had told a representative of the Kirk campaign of her concerns when the campaign contacted her on Thursday to try to verify Mr. Kirk’s time at the nursery. She said she had spoken to the teacher who led what was then a play group that met in the church basement. The teacher had a “vague recollection” of having him as a work-study student, Ms. Grubb said, but she did not remember his name. She added that Mr. Kirk did not have major responsibilities at the play group, like creating lesson plans, and he was assistant who played with the children.

The campaign of the Democratic Senate nominee in Illinois, Alexi Giannoulias, first raised questions with The Times about Mr. Kirk’s classroom experience. Mr. Giannoulias has also faced questions about his background and his ties to the federal seizure of his family’s bank in Chicago.