It may depend on your wall construction - can you tell us more about how the wall is constructed.
As a general rule the vapour barrier (i.e.: your plastic membrane) wants to be on the warm side of the insulation.
But in the first post you will find the following "Note the golden rule of walls: The Vapour Barrier goes on the warm side of the insulation!!!!. The vapour barrier in this drawing is the OSB, which is full of glue and therefore highly resistant to the passage of moisture." Exactly as celston also told you.