That’s putting it mildly: I’m entirely aware that there’s a concerted campaign in the UK to smear Corbyn by fabricating a story from out-of-context quotes and, despite not being a fan of Corbyn, I’m entirely on board with the idea that he’s being unjustly targeted and probably isn’t actually antisemitic. But so far there’s no evidence that Israel is behind this effort. A more likely explanation is that he’s a thorn in the side of the Tories and the conservative-leaning establishment media, and the campaign successfully undermined Labour’s (and specifically Corbyn’s) public support (which the polls clearly reflect: they’re losing out agains the most incompetent and least-liked UK government this generation has seen).
There’s no need for Israeli operatives to get involved, and considering the potential fallout if this got out, it would seem to be a risky undertaking. Much easier to publicly denounce Corbyn, as both Netanyahu and the Israeli ambassador to the UK have done (along with the Foreign Ministry, if I remember correctly).