What is the test for abuse of process?

On the hearing before us the primary contention made on behalf of the respondents is that to allow this collateral attack now to be made is an abuse of the process of the court. It may be said that the doctrine of res judicata is a species of abuse of process, but abuse of process may be found in cases not strictly res judicata. We refer to the comments of Lord Diplock in Hunter v. Chief Constable of West Midlands and Another, [1981] 3 All E.R. 727, 729 and 733 who speaks of the court’s inherent power to prevent manifest unfairness. Proceedings which are frivolous, vexatious or oppressive are abuse of process: 9 Halsbury (4th Ed.) para. 38. These proceedings will fall within that class if the matter should have been litigated in the earlier proceedings, or, as a collateral attack on an earlier determination, are not likely to succeed.