Your duty to warn your client if your advice is based on incomplete or inaccurate information
Your duty to warn your client if your advice is based on incomplete or inaccurate information arises under section 961H of the Corporations Act. ASIC discusses it in paragraphs RG 175.359 to 362.
For obvious reasons if a professional person believes a client is not telling the truth is not telling the complete story then he or she should take appropriate action. One would expect a reasonable financial planner concerned that a client was withholding information would either decline to advise or would include an extensive warning in the advice, in effect disclaiming responsibility.