Rabbi Charles Wallach has brought forward his retirement at cash-strapped Brighton and Hove Reform Synagogue.
Chairman Michael Harris has informed members that the minister will leave his full-time employment at the end of April, although he will act as consultant rabbi on a freelance basis.
Although the shul has 500 adult members, many are elderly and 150 pay reduced subscription rates. Membership has dropped from 600 at the end of 2009. The number of children in the community has remained constant at around 100.
"It was the rabbi's decision to take early retirement," Mr Harris said. "This followed discussions about the synagogue's financial position. His decision has been supported by the board." In September last year, the board identified an ongoing deficit of £35,000. "We can't go on like this."
The shul has reserves of £150,000 but its 1960s building in Hove's Palmeira Avenue will require major repairs within the next few years, including a roof replacement. "We don't know where the money is going to come from," Mr Harris said.
Rabbi Wallach, 62, was "sad that the synagogue's financial situation forced a curtailment of my contract. I thought very carefully about the offer of a part-time position but decided to continue to be available to the synagogue as a freelance rabbi for the immediate future."
Thanking Rabbi Wallach and his wife for their contribution, Mr Harris said a part-time replacement would be sought.