Murray Clearsky, former grand chief of the Southern Chiefs' Organization, says he has receipts for many of the expenses and can justify them.
But he says he was never given a chance to repay the money or explain the expenses to federal auditors.
In a letter to the organization, Aboriginal Affairs says auditors found $261,000 in questionable spending — just over half the federal funding the organization receives.
The letter highlights almost $39,000 withdrawn on a debit card during a trip to Minneapolis, as well as more than $5,000 racked up during a trip to Las Vegas.
Current Grand Chief Terrance Nelson says the federal government is using audits like this to target aboriginal organizations that are seen as unfriendly.