MASON C.J., BRENNAN AND GAUDRON JJ. The answer to the applicants' case for relief in this Court is that the decisions of which the applicants complain have been made in the course of the exercise by the Full Bench of the Industrial Relations Commission ("the Commission") of the wide discretionary powers conferred upon it by the Industrial Relations Act 1988 (Cth) ("the Act"), particularly ss.110 and 111, with respect to the procedure to be followed in the hearing and determination of matters before it. Questions relating to the joinder of proceedings with the same or related issues, whether such proceedings should be heard together, successively or separately, and the order in which they are to be heard are issues which ordinarily and frequently arise in the exercise of the Commission's jurisdiction. They are not questions which go to the existence of jurisdiction.

2. Furthermore, nothing has emerged in the present case to indicate that what the Full Bench has done is inconsistent with the duties imposed upon the Commission by the Act. So far as the arbitral proceedings are concerned, they had passed beyond the stage of conciliation. The Full Bench was therefore entitled, if not bound, to resolve them by recourse to arbitration in accordance with the Act. The Full Bench was under no duty to deal first with the certification proceedings in which the applicants sought certification of agreements with certain of their employees under s.115. As we have already indicated, the order in which the proceedings were to be heard was a matter for the Full Bench to decide as a matter of discretion.

3. Section 111(1)(g)(iii) confers a discretion on the Commission which is to be exercised in the light of the relevant facts and circumstances as they bear on the public interest. Ascertainment of where the public interest lies is very much a question of fact and degree ((1) Re Queensland Electricity Commission; Ex parte Electrical Trades Union of Australia [1987] HCA 27; (1987) 61 ALJR 393, at p 395; 72 ALR 1, at p 5.), but the public interest in the question whether further proceedings of an arbitral kind are not necessary or desirable is not necessarily identical with the public interest in the question whether agreements should be certified under s.115. Therefore the question whether the agreements in the present case should be certified was relevant to but not conclusive of the question whether the arbitral proceedings should be continued. The power conferred by s.111(1)(g)(iii), if exercised, is one which defeats a prima facie right to have jurisdiction exercised ((2) Re Australian Bank Employees Union; Ex parte Citicorp Australia Ltd. [1989] HCA 41; (1989) 167 CLR 513, at p 517.). It is therefore a power to be exercised with due circumspection on a proper consideration of the relevant materials. However, when a party makes application for an exercise of the power, the Commission must afford the applicant a reasonable opportunity to allow his or her case to be put and, in appropriate circumstances, mandamus will go to enforce that obligation ((3) ibid., at p 520). This does not mean that the Commission has no discretion to decide when it will deal with the application. The Citicorp Case does not deny the existence of such a discretion. Mandamus was granted in that case because there was a refusal to exercise the power based on the erroneous view that it could be exercised only after a finding of dispute.

4. The case for relief here falls far short of a refusal to embark upon an exercise of the power. The Full Bench recognized the existence of the power and gave comprehensive consideration to the arguments telling in favour of and against the exercise of the power, concluding ultimately that the Commission should not refrain from exercising the principal jurisdiction conferred by the Act. Accordingly, there was no actual or constructive refusal to exercise jurisdiction under s.111(1)(g)(iii).

5. The decision not to allow the applicants to call further evidence did not, in the circumstances of this case, amount either to a refusal to exercise jurisdiction or to a denial of natural justice. It was, we think, for the Full Bench to determine, in the light of the knowledge which it already had of the history and facts of the relevant proceedings, whether the evidence which the applicants sought to tender would throw light on the issues which fell for decision. In that respect, the Full Bench was prepared to make certain assumptions in favour of the applicants for the purpose of dealing with the application under s.111(1)(g)(iii). They were: (1) that jurisdiction existed under s.115 to make the certification order sought; and (2) that the agreements were capable of being certified. In its decision on the s.111(1)(g)(iii) application, the Full Bench said:

"In the course of the present proceedings, the Commission

indicated that for the purposes of the s.111(1)(g)

application we did not require to hear further submissions

or evidence from the Hoyts Group in relation to the question

of jurisdiction concerning the s.115 agreements or matters

relating to compliance with the requirements of s.115.

Although we make no ruling at this stage about these, for

the purposes of this decision regarding the s.111(1)(g)

application we have assumed that the various s.115

agreements between the Hoyts Group and employees meet the

requirements of s.115 and are capable of being certified by

6. On the basis of the Full Bench's willingness to make these assumptions as a foundation for its consideration of the application, we conclude that the Full Bench's decision not to receive the evidence did not amount to a denial of natural justice or a refusal to exercise jurisdiction. In reaching that conclusion, we are mindful of what the Full Bench said in giving its reasons for refusing the application under s.111(1)(g)(iii). The Full Bench observed:

"It is doubtful, in our view, that the certification of

the s.115 agreements will resolve all the matters in dispute

which are before the Commission in the present proceedings.

We adopt this view because the two unions involved in the

proceedings are not party to any of the agreements and the

agreements have not been entered into by all relevant

employees of the Hoyts Group."

"Despite what has been put (by) the Hoyts Group we do not

consider, having regard to the history of the present

matters and disputes before the Commission, that all the

matters in dispute between the parties to the proceedings

will be resolved by the certification of the s.115

agreements. We believe it would not be appropriate,

as a matter of discretion based on public interest

considerations, to make any of the orders sought by the

Hoyts Group to stay part of the present proceedings on the

basis of developments regarding the s.115 agreements."

"We have not been persuaded, on the basis of the

submissions or material presented by the Hoyts Group in

support of the s.111(1)(g) application, that we should make

any orders to dismiss or refrain from hearing the unions'

applications for the making of awards. However, apart from

this, we do not consider that the public interest would be

served in the circumstances of the present matters and

disputes by allowing one party to overturn the orderly

process established by the Commission directed towards

allowing relevant issues, arguments and material in relation

to the present matters and disputes to be presented by all

parties and considered by the Commission."

The Full Bench then referred to its earlier decision in which it said:

"We would add that no ruling has been made by the Bench

which prevents the parties from referring to the s.115

agreements and their implications etc. during the course of

their submissions in the present matters. Indeed we note

that the agreements have been raised in the examination and

cross-examination of witnesses called in these proceedings"

and went on to say that it would be open to the Hoyts Group to raise the question of joinder again and, if it did, the Commission would consider and rule upon it.

7. Although the effect of the statements quoted above is not altogether clear, we consider that the Full Bench was stating that the public interest issues, including those arising out of the applications made under s.115(4) and the issues advanced in relation to the respondents' claims, remain for determination before the Commission proceeds to make final awards. It is, of course, open to the Commission even now to give consideration to the exercise of its power under s.111(1)(g)(iii) on the basis of appropriate public interest considerations. If we have misinterpreted the Full Bench's statements and it does, in fact, regard public interest issues as foreclosed by the rulings that it has already made, the applicants will be able to take appropriate steps with a view to rectifying that situation.

8. There is one remaining issue concerning the application under s.111(1)(g)(iii). The applicants contend that, having regard to the assumptions made by the Full Bench when it rejected the application to call further evidence, nothing remains to be determined in the arbitral proceedings. This submission is based on the effect which is given to a certified agreement by s.116. However, in the light of the matters which remain open for determination and which were identified in the Full Bench's ruling on the application under s.111(1)(g)(iii), we do not think that the applicants' contention can be sustained.

9. Finally, it is said that, as a matter of implication, s.116 of the Act has the effect that applications for certification must be dealt with before the Commission exercises arbitral powers with respect to the matters dealt with in the agreement.

10. Section 116 relevantly provided:

"(1) While a certified agreement is in force:

(a) the terms of the agreement prevail over the terms of

an award or an order of the Commission binding on the

parties to the agreement that deals with the same

matters;

...

(e) the Commission shall not exercise arbitration powers in

relation to the matters dealt with in the agreement."

11. The argument with respect to s.116 must fail. There is no basis for an implication extending the operation of the section beyond its clear terms.

12. The applicants' motion is therefore dismissed.

Motion for writs of prohibition, a writ of certiorari and writs of mandamus dismissed.