After a bit of research on the posted replies, i found that if too high values of resistances are used on such high voltages then, noise will be generated, and if too low, then divider network will start loading the main line un-necessarily. I think that following solution will be ok
220V will be stepped down on a separate line to about 6V (This procedure is just for measurement), then it will be passed through a voltage divider, following which is the isolator chip. Across the isolator, ADC will be waiting for the voltages.
Any suggestions are most welcome