The leader of Preston City Council, Peter Rankin, is to take a leave of absence because of ill-health.
Coun Rankin will have surgery next week for a brain tumour, councillors were informed at the town hall on Thursday.
Deputy leader Coun Robert Boswell will step up to the lead role in his absence, the council said.
In a statement read to elected members at the full council meeting, Mayor Brian Rollo said Labour leader Coun Rankin hopes to be back for the local authority's budget meeting in February.
Mayor Rollo said: "I have to tell members that the leader will be taking leave of absence from the council, from December 22 for health reasons.
"Specifically he will be having surgery next week for a brain tumour.
"For the next two months he will be having further treatment and be in recovery. I know he hopes to attend our budget meeting on February 22.
"During this period his deputy, Coun Robert Boswell, will act on his behalf, with the support of cabinet.”