When finishing a portion of a basement:
Is it OK to put 1" foam board against the poured concrete wall, then build the 2x4 wall and then insulate it. Is a vapour barrier needed?

Thanks

ONLY if you foundation is totally dry after a plastic test (and the foam board acts as a vapor barrier as long as the seams are very well taped). https://www.thisoldhouse.com/how-to/how-to-frame-out-basement-walls

If it isn't, and many aren't, you have to build the wall out from the concrete. There are videos showing how.

Thanks for your reply.
I actually saw this and another video on familyhandyman I think.
I was 2nd guessing after debating with a couple of carpenters I know.