Doncaster is without a civic mayor for the first time in decades after Coun Margaret Pinkney stepped down due to ill-health.
It is understood Coun Pinkney has not carried out an official function since October because of her health and has now been forced to resign from the high profile ceremonial post with immediate effect.
Councillors are due to meet next month to decide what to do to fill the post until the next mayor is appointed in May at the annual meeting.
A temporary appointment may be made in the meantime.
The current deputy, Coun Eva Hughes, has been carrying out duties in Coun Pinkney’s in recent days.
Coun Pinkney, and Independent member, has carried out the high-profile post, which also involves acting as the chairman at full council meetings, since she was appointed last year.