Graham Harrison has stepped down as leader of Hartlepool Borough Council less than four months after taking up the position in May.
The Reform UK councillor, who represents Burn Valley ward, announced his resignation on Monday. He said a recent change in his personal circumstances means he is "no longer able" to commit the required time to the role.
In a statement, Harrison said: "The role is, in effect, a full-time commitment and I do not believe it would be right to continue if I cannot give it the time and attention it deserves. This has been a very difficult decision and certainly not one I have taken lightly, however I believe it is the right decision both for me personally and for the council."
What happens next
A new leader will be appointed at an extraordinary meeting of the council on 15 September. Harrison will continue as a councillor representing Burn Valley ward.
Reform UK holds 15 seats on Hartlepool Borough Council following the May election, which gave the party more seats than any other group. Labour holds 14 seats and Independents hold seven.