No, you do not need to have a demat account with a lender to get a loan against securities/shares (LAS) with the same lender.

This means that you do not need to have a demat account with ICICI Bank to avail of a loan against shares (LAS) with it. You could have a demat account with any Depository Participant (DP) in NSDL or CDSL and get a LAS with another provider.