Wider duty of a lawyer

My friend, who is now attempting the final part of his training to be a lawyer, made this statement, "The duty of a lawyer is to protect the best interest of his client".

I asked him if the lawyer has a duty to uphold the integrity of the legal process. For example, is it all right for a lawyer to act for the client in the following actions?

a) writing a prospectus that is confusing to the public?
b) arranging an investment scheme that defrauds the public?
c) intimidating the public with defamatory action without sufficient grounds?
d) helping the client to draft untrue statements?

e) drafting legal contracts that are unfair to the customers (i.e. possible contravention of the fair trading act)?

My friend found it difficult to answer my questions. The law is not clear on these matters. There are insufficient case history to rely on.

I will be asking the Law Society on these ethical questions. I hope that they can provide some guidance to their members who are practicing lawyers.

Tan Kin Lian