The practice of moving patients from bed to bed in hospitals increases the chance of infection being spread, the BMA has said.
The trend follows a falling number of beds due to increasing ward closures, according to the British Medical Association (BMA) Cymru Wales.
But the organisation warned that with overcrowding leading to three or four patients using the same bed one after the other, the risk of passing on infections such as Clostridium difficile was more and more likely.
Other drawbacks to constantly swapping beds include the confusing effect it has on patients - particularly elderly ones - and the difficulty it causes for visitors trying to find relatives.
The group admitted that even doctors can have difficulty tracking down patients who are moved between wards.
The average number of NHS beds available daily fell every year between 1997/98 and 2007/08 from 15,194 to 13,354. In the same period the occupancy rate rose from 78.7% to 82.8%, peaking at 83% in 2003/04 and 2004/05.
Dr Stefan Coghlan, chairman of the BMA’s Welsh consultants committee, said: ‘This is putting an intolerable strain on staff and causing a great deal of stress and confusion to patients.
‘We certainly wouldn’t be able to cope in a crisis. It is just unsustainable.’