No officer, whether elected or appointed, or any employee, whether full or part time, of the City shall have a substantial financial interest, direct or indirect, in any contract, or other procurement process, a substantial financial interest, direct or indirect, in the sale to or purchase from the City of any land, materials, supplies or services, except on behalf of the City as an officer or employee. The words “substantial interest” as used herein shall be defined in Chapter 171 of the Local Government Code. Any willful violation of this section shall constitute malfeasance in office and any elected or appointed officer or employee found guilty thereof shall thereby forfeit his office or position. Any violation of this section with the knowledge, express or implied, of the person or the corporation contracting with the governing body of the City shall render the contract or other procurement process involved voidable by the City Manager or a majority vote of the full membership of the City Council.