Can a plaintiff amend their statement of claim to add a new cause of action?

Therefore, in the first suit the plaintiff should have liberty to move for an amendment of the general sort in question here, subject to the discussion below of evidence and more precise wording. There are two ways that that permission to amend the statement of claim late might be properly justified. One is an exception to the rule against adding new causes of action where there are special circumstances: Basarsky v. Quinlan 1971 CanLII 5 (SCC), [1972] S.C.R. 380, [1972] 1 W.W.R. 303, 24 D.L.R. (3d) 720. The second is as a term or corollary of leave to amend the statement of defence in the first suit late. It is not necessary in this appeal to decide which is the better explanation. These two possible rationales differ somewhat from that of the chambers judge.