Someone (I'm too lazy to go back and find out who) called Ewan McColl's singing twee.
As I see it, his renderings of traditional ballads, chanties, and so forth are anything but twee. Many (maybe not all) of the songs he wrote for his own singing seem a bit over the top to me, not in the singing but in the song itself. This may be related to the political or polemic nature of so many of his songs.
I'm sure there are other singers where a similar comment may be made.