Democratic Rep. Martin Frost (search) canceled a campaign appearance with Peter Yarrow (search) over the folk singer's 1970 child indecency conviction, and Republicans are challenging the congressman to return the money already raised for the event.

Yarrow, a member of the group Peter, Paul and Mary (search), was convicted of "taking indecent liberties" with a 14-year-old girl in 1969. President Carter pardoned him in 1981.

Frost said in a statement that "crimes against children are very serious offenses."

"I do not believe it is appropriate for Mr. Yarrow to campaign on my behalf," the congressman said.

Frost, who faces Republican Rep. Pete Sessions (search) for a Dallas-area congressional seat in November, often mentions his role in the Amber Alert and anti-child abduction legislation.

Frost's campaign said there are no immediate plans to refund money already raised for the Oct. 11 fund-raiser, which will be held as scheduled. Tickets cost $250 to $1,000.

"To keep this money, especially when you're out there in television ads as the protector of all children, is just the height of hypocrisy," said Chris Paulitz, spokesman for the National Republican Congressional Committee. "You don't keep money that comes from a child molester. This is politics 101, this is human decency 101."

Sessions challenged Frost to either return the money or donate it to a charity for sexually abused children.

"For at least several weeks, Martin Frost has been raising money off an event that was bringing a convicted child molester to town," Sessions campaign manager Chris Homan said.

Yarrow has been active in politics and other social causes for years. He appeared in Iowa for John Kerry before the presidential primaries.