Councillor Edith Bald, leader of the Conservative Group at Milton Keynes Council will not be seeking re-election as leader of the Conservative group for the new council year.
A new leader will be elected at the annual Conservative group meeting on May 13.
Councillor Bald said “It has been a huge privilege to serve as leader of the group for three years and something that I have enjoyed enormously.
“Our group has gone from strength to strength, gaining four additional seats in the three years and narrowly missing becoming the largest political group on the council in 2016.
“However leading the Group is a demanding and very time consuming role and I have decided that it is the right time to allocate more time to family and retirement.”
She added: “I will be staying on as a ward councillor and still playing a full role in the group.”