This quote from Gomery's Report.
The Minister of Finance establishes the fiscal framework within which overall government spending takes place. Once that framework is set, departments are responsible for the management of the expenditures allocated to them, with general oversight by Treasury Board. The Department of Finance and its Minister have no oversight role for other departments' expenditures, other than setting the financial context via the fiscal framework. The Minister can spend money only after Parliament has approved the spending, and it is primarily the role of that department to ensure proper management and compliance with legislation.
So, because Martin as the Minister of Finance did not have any form of "oversight role," he cannot be considered complicit in the Sponsorship Program.