POGS, in regard to your post @14:55 yesterday, then your guess would be as good as mine. However, in stating they would resign if Rebbeca Long-Bailey is elected as leader it has to have come from right wing MPs within the party.
In the above, and if I were a betting man, my money would be on Margret Beckett, Margret Hodge and the small group who have been in league with those two in recent times.
Hodge would certainly have the connections into the right wing press especially "the Times" where I believe this story first emerged before the "Red Tops" gave it more prominence.