Exhibit 23(a) CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS As independent public accountants, we hereby consent to the incorporation by reference in this registration statement on Form S-8 of our report dated January 25, 2001 incorporated by reference into the MDU Resources Group, Inc. Annual Report on Form 10-K for the year ended December 31, 2000, and to all references to our Firm included in this registration statement. /s/ ARTHUR ANDERSEN LLP ARTHUR ANDERSEN LLP Minneapolis, Minnesota June 13, 2001