On 25 June 2014, the Senate agreed to a resolution related to a range of matters concerned with estimates hearings, confirming:

• previous resolutions that there are no areas in connection with the expenditure of public funds where a person has the discretion to withhold details or explanations from the Parliament or its committees unless the Parliament has expressly provided otherwise;
• that an officer shall not be asked to give opinions on matters of policy and shall be given reasonable opportunity to refer questions to a superior officer or the minister;
• that any claim to withhold information must be on an established ground (noting the Senate Order of 13 May 2009 which sets out the proper process for raising public interest immunity claims);
• the statutory values which Australian Public Service agency heads and employees are required to uphold which include a requirement to be open and accountable; and
• the constitutional framework of checks and balances which places the Parliament in prime position as the agent of accountability.

The full text of the 2014 resolution and the earlier resolutions referred to in it can be found here:

• Accountability and estimates hearings - resolution of 25 June 2014
• Privilege Resolution 1 – Procedure to be observed by Senate Committees for the protection of witnesses
• Witnesses – powers of the Senate
• Public interest immunity claims
  • Chapter 19 of Odgers’ Australian Senate Practice (14th ed) provides a comprehensive guide to the operation of public interest immunity procedures.
• Answers to questions on notice provided on time
• Obligations to the Senate and FOI
• Additional hearings on Fridays 
• Additional hearings generally