This got resolved with the prefix list filter incorrectly configured. Added allow all on prefix filter on inbound list filter and now traffic flows through the BGP routes.
An additional concern is, we receive default route i.e. 0.0.0.0/0 from the ISP and some prefixes from another peer group. I have given weight of 1 to ISP neighbor and weight of 10 to peer group. Still majority of the traffic to the routes available from the peer group flows through the default routes. Please suggest, if any further changes required on this.
Thanks