Another pic attached showing the wall behind a dressing table. The wall is made of brick with a cement render which was then painted using water based emulsion paint.
It is a first floor room there is no drains or pipes on the other side although it is a gable wall. The apartment is in Lahore, Pakistan which has very hot summers and little rainfall in the year and is not located near the sea.
If I were to bring back a sample of the white growth is there somewhere in the UK I could get it analysed?
Going by the colour, it doesn't look like rot or fungus to me. I'd guess it's the result of a chemical reaction between the top layer and the substrate, possibly assisted by moisture.