London Health Emergency (LHE) issued the warning after the announcement that the hospital was closing the Chapel Ward, which provides short-term care for patients, at the end of the week.
LHE spokesman Geoff Martin said: "There really is a danger that if you close nearly a quarter of the hospital's beds it will place extra pressure on the emergency beds at Kingston and West Middlesex hospitals."
Mr Martin said the ward closure flew in the face of a government drive to increase the number of short stay care beds available at hospitals like Teddington.
But a statement released by the Teddington Memorial Hospital NHS Trust said the decision to close the ward followed a review of staffing levels.
Trust chairman Pamela Bryant said: "It is utter nonsense for anyone to suggest that the future of the hospital is not secure or it is under threat of closure.
"Nothing could be further from the truth."
The trust has pledged to make the beds available during the winter and when necessary to ease the pressure on the emergency departments at Kingston and the West Middlesex Hospital.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article