@vidhya_mouli 

if you are talking about Consumer Portal (csp), then it's for snc_external users usually the Consumers etc.

Since those are not sys_user records you cannot add impersonation logic there.

Why would 1 consumer impersonate another one?

I already informed above i.e. it doesn't look like a valid business requirement.

If my response helped please mark it correct and close the thread so that it benefits future readers.