"x x x.
Since the court has no jurisdiction over the complaint and respondent, petitioner is not estopped from challenging the trial court's jurisdiction, even at the pre-trial stage of the proceedings. This is so because the issue of jurisdiction may be raised at any stage of the proceedings, even on appeal, and is not lost by waiver or by estoppel.
The ruling in People v. Regalario that was based on the landmark doctrine enunciated in Tijam v. Sibonghanoy on the matter of jurisdiction by estoppel is the exception rather than the rule. Estoppel by laches may be invoked to bar the issue of lack of jurisdiction only in cases in which the factual milieu is analogous to that in the cited case. In such controversies, laches should have been clearly present; that is, lack of jurisdiction must have been raised so belatedly as to warrant the presumption that the party entitled to assert it had abandoned or declined to assert it.
In Sibonghanoy, the defense of lack of jurisdiction was raised for the first time in a motion to dismiss filed by the Surety almost 15 years after the questioned ruling had been rendered. At several stages of the proceedings, in the court a quo as well as in the Court of Appeals, the Surety invoked the jurisdiction of the said courts to obtain affirmative relief and submitted its case for final adjudication on the merits. It was only when the adverse decision was rendered by the Court of Appeals that it finally woke up to raise the question of jurisdiction.