Help in 325watt SMPS design

Regarding Hi-Pot testing failure issue....

Our SMPS is working fine at 1.4KVac on Hi-pot testing but it fails at 1.5KVac.

Please suggest us useful modifications in layout & capacitor values in filter section.

That is impossible as nobody knows what the current layout is? Even knowing the layout nobody can actually see your board and know the relative test conditions like RH and Ambient Temp. Hi Pot failure and you make no mention of the leakage current? It is impossible to answer your question. What about board material?

Ron