South Buckinghamshire Golf Club said removing nine holes would mean the new layout would “more than likely not have an official course rating any time soon”.
It added, without a recognised course rating, formal competitive play and handicap qualifying golf could not take place.
Club Chairman Michael Murphy said members had been given just six weeks’ notice that half of the golf course would be taken out of play.
Last year they were assured that the site would remain open as usual during the design and planning process, he said.
“We believe it is important that the impact on the established sporting community is properly taken into account before a drastic decision to let half a golf course effectively go fallow and unused is enacted.”
The football club said use of the golf course had declined and was “no longer financially viable”.
It added it planned to introduce new facilities such as a driving range and argued the nine-hole format would be “a more flexible way to play”.