I have an ongoing problem in a flat. The bathroom ceiling have been re-plastered twice but as I suspect, damp patches continue to seep through. I have no control over the room above and have been told there is no leak coming from their property (which of course may not be true). Can anyone suggest another cause, from experience? Could this damage the building structure and although not exclusively a DIY question how has anyone dealt with this problem.

for info the building is Victorian and 'management' have not been able to deal with the issue.

From the photo, I would guess that your problem is one of condensation.
Years ago, homes suffered from condensation on a regular basis.
The solution at the time was to paint bathroom and kitchen walls and ceilings with gloss paint.
Two or three coats of gloss paint are almost water vapour proof, and painting attenuated the amount of water vapour entering the plaster and stopped the problem.
These days, we solve the problem by fitting extractor fans and using them while washing/showering and perhaps letting them run for a time afterwards.
The best solution is to fit an extractor fan complete with heat exchanger, shutter, and humidity control... having a shutter will keep out the cold wind....having a humidistat means the extractor will come on when needed and turn off when its done its job, its cheaper to run as well.

thanks for the reply. The bathroom has not been used for quite a long time, some of the appearance may be due to re-plastering. when it was previously painted, the water stain only appeared on the ceiling. there is an extractor fan fitted, but there may be inadequate heating.