This is so irritating.
The Brexit party is in a massive lead. If you add UKIP and the Conservatives it is close to 50% votes for Leave. If you add Lib Dems and Greens (after all, as you and everyone else in this thread have said, Labour is a brexit party), it is *not* close to 50% for remain.
The fallacy is that there is some mass of Remain voters waiting to jump ship to Labour in a parliamentary election, which can offset Leave losses, and I just don't see it.
They might well do better, there's no guarantee of it (they might do worse too). There's also no guarantee that a second referendum wouldn't be Leave again.