In a statement today, the consultancy said that Tant will step aside after ten years in the role to make way for Mark Sitch, currently a senior planning partner at the firm’s Solihull office.
A spokesman for the firm said the move was a "natural handover".
The firm said that Tant would continue as senior planning partner in the Reading office, focusing on fee-earning work and business development.
It added that Sitch joined Barton Willmore in 1999 and has more than 20 years of private sector experience in promoting and advising on the delivery of large and complex sites.
Sitch said: "This is a hugely exciting time for the business and I am delighted to have been chosen by my fellow partners to lead the practice.
"Ian achieved a huge amount in his ten years as senior partner and I am pleased that he will continue to play a key role in our Reading planning practice.
"Planning for growth is now at the heart of the political agenda and as the foremost independent planning and design practice we have the national expertise and local knowledge to help deliver the new homes, jobs and infrastructure the country needs."
Tant said: "I am immensely proud of my tenure, having led the practice through both high times and the depths of the recession, while maintaining a high quality of service and a strong market position throughout.
"Mark will bring fresh drive and energy to the role: I congratulate him on being elected by the partners and wish him every success."
Sitch will take up the new role on 1 January 2015.