REGINA - Saskatchewan Premier Lorne Calvert has asked the conflict of interest commissioner to investigate how an apparent case of fraud in the NDP caucus office was handled 15 years ago.

The controversy involves a caucus worker who left her job in 1992.

The worker wrote a letter to then caucus chair Glenn Hagel and caucus chief of staff Jim Fodey confessing that she had inflated expense cheques.

Hagel, who is now government house leader, has said the letter along with the results of an audit were promptly taken to police to be investigated, but police say that wasn't the case.

Fodey resigned on the weekend and the Opposition Saskatchewan Party has been calling for Hagel's head.

Calvert says Hagel volunteered to resign but the premier rejected that offer.