Councillor Matthew Atkins, who took on the role after May's local elections, has stepped back from it. He will remain a Cosham councillor.
This was confirmed by the council's chief executive on Tuesday, however no reason for his departure from the leadership position has been given. His successor will be elected this week.
Cllr Atkins, who was first elected to the council in 2019, and was re-elected to his seat in May, took over the leadership role from Donna Jones in May after she became the police and crime commissioner for Hampshire.
But less than four months later, Cllr Atkins has already left the position. No reason has been given for his departure with no Conservative councillor responding to requests for comment.
The news was confirmed by the council's chief executive, David Williams, in an email to councillors on Tuesday morning.
‘I have been notified that councillor Matthew Atkins has ceased to be Conservative group leader,’ he said.
‘Ryan Brent, as deputy group leader, will be acting as interim group leader until such time as a new Conservative group leader is elected.’
No one from the council's Conservative group was available to comment on the reasons for the change in leadership.
Cllr Atkins would say only that a meeting will be held on Friday at which his successor will be voted in by the group’s elected representatives.
Councillor Gerald Vernon-Jackson, the Liberal Democrat leader of the city council, said he was looking forward to working with the new Conservative leader.
‘I wish Matt well and hope we can move on and work more closely with the Conservative group,’ he said. ‘We want more cross-party working as that will be far more beneficial for the people of Portsmouth.’