Labour MP Preet Gill criticised the decision, stating that the people of Warwickshire "deserve better" and that the role is "not work experience."
Reform UK councillor Finch secured the leadership after a tie vote with the Liberal Democrat nominee, Jerry Roodhouse, which was broken by the council's chair, Edward Harris.
The appointment occurs amidst recent turmoil for Reform UK, including several councillor resignations post-local elections and suggestions from a leading pollster that the party's support has "topped out."