According to CAB information;(posted 7848 days ago)the bank has a "duty of care" towards the client when selling the property. This means that the lender must get the best price that can be reasonably obtained at the point at which it sells the property. However, in practice, lenders often sell properties at auctions for less than would if sold on the open market.
A lender who sells a property without due care could be sued for negligence. However, this has never (apparently) been tested in the courts. There may also be a claim for negligence against the estate agent used by the lender, but this can be very difficult to prove.