Increasing dampness on walls is because of capillary action, owing to lack of DPC or DPC failure.
Solution in Existing Homes
Remove the existing plaster from damp surfaces, rack off all brick joints to remove loose mortar, clean & wash the area; refill the brick joints with Polymer modified cementitious (PMC) mortar (Tapecrete P-151: Cement: Silica Sand/ Fine sand = 1: 2: 4-6 by weight); apply two coats of Tapecrete slurry (Tapecrete P-151: Cement = 1: 2 by weight)& re-plaster the wall with cement-sand mortar admixed with CICO Super.
Solution in New Homes
Go for damp proof course in foundation. Add CICO No. 1 in concrete before casting concrete foundation layer on soil. Lay brick walls upto ground level with cement-sand mortar admixed with CICO No. 1. Then lay a DPC layer of 25 mm thick concrete admixed with CICO NO 1,apply two coats of Tapecrete slurry (Tapecrete P-151: Cement = 1: 2 by weight) on it and then construct the brickwork in superstructure .