The move leaves the loss-making station in the hands of UBC, which has already said it has written off its investment and was looking at ways to exit the venture.
However, UBC has been unable to find a buyer for the Oneword Radio. It is now winding the station down, because it has decided it cannot continue bearing the losses, according to UBC chief operating officer Jon Quinn.
He said: "At this point in time it doesn't look as if there is a future for Oneword, which is very unfortunate.
"It was one of the few original formats to launch on Digital One [the first national digital radio multiplex]."
The station's output has been scaled down, and its website now has a holding page saying: "As you may have read in the press, the future of Oneword has been uncertain for some time now. We are carrying out a strategic review which should see a resolution in the New Year."
The speech and books-focused station was launched in 2000, but its latest Rajar audience figures give it a weekly reach of only 138,000 listeners.
Channel 4 was unavailable for comment at the time of publication.
Channel 4 is launching its own speech-focused station, Channel 4 Radio, on the new digital radio multiplex that comes into operation next summer. The station itself will not begin broadcasting until January 2009 and may not fully launch until April 2009.