The leader of Hastings Borough Council, Jeremy Birch, has been taken ill.
He was taken to hospital on Friday, May 1.
Kevin Boorman, spokesman for the council, said councillor Peter Chowney, who is deputy leader, has stepped in as acting leader of the authority until further notice.
He said: “Cllr Jeremy Birch remains seriously ill in a coma in hospital. Our thoughts are with his family.
“Deputy leader Cllr Peter Chowney will be covering his duties until further notice.”
Cllr Birch is a long-standing councillor on the borough council and has been so for the last 17 years.
Since May 2009 he has been been county councillor for the Old Hastings and Tressell ward.