It has been unable to find a buyer for the local television station.
The Manchester-based station will remain on-air but from Friday will no longer broadcast its evening magazine show, Channel M Today, and cease production of all original news and features.
GMG issued a statement today saying that despite interest from "a number of parties" a viable offer for the station had not emerged.
The operation of the station had been under review following the sale of GMG's 32 regional newspapers, including the Manchester Evening News and its associated titles, to Trinity Mirror last month.
The £44.8m deal saw Trinity Mirror pay £7.4 in cash and release GMG from an obligation to pay a further £37.4m owed on a long-term print deal; however Trinity was not interested in taking control of Channel M making its future uncertain.
GMG said today: "We have reached the conclusion that the station is no longer sustainable in its current form.
"This is due to a number of factors, including the absence of a committed buyer, the loss of access to news from MEN Media, and the costs associated with the requirement to leave the Urbis building.
"As a result, from this Friday the station will no longer broadcast evening magazine show Channel M Today, and will cease production of original news and features video.
"Channel M will remain on air, focusing in the short-term on a mixture of archive material, traffic and networked news."
As a result of the changes Channel M will retain just four of its 33 staff; the company said it had entered consultation with those affected.
GMG said it would remain the owner and operator of both Channel M and the associated Freeview multiplex business in Manchester.
The remaining staff will oversee the schedule; manage the transmitter and Freeview multiplex business.
Oliver Luft writes for Press Gazette.