weird crease when smooth shading

Hey everyone, I was wondering if you could tell me why this is happening in the model?

It has a mirror modifier then a subsurf modifier as well.
I have tried reversing the normals, making the normals consistent, removing double verticies, mucking around with the mean crease and nothing seems to change it.

Any suggestions?

I suggest you post the blend file in such cases.

It does look like a normals thing, or possibly internal faces.

Did you attach the head as a separate object?

Nah I didn’t thats the weird part. although after extruding the neck there were faces i deleted before I continued modelling the rest of the body (which is exactly where that seam is!)

In this order:
Remove any internal faces
Remove doubles (W/remove doubles)
Recalculate normals (Ctrl+N)
If still not correct, display your face normals (N/display panel in edit mode) and manually flip those that are not correct (W/flip normal)

Can you post a shot of your wireframe of that area? You may have nearly-coincident edge loops, in addition to the other suggestions. One way to check is to select the loop at the problem crease, then expand the selection once using CTRL+NUMPLUS. If the selection doesn’t immediately jump to the next adjacent (and well-spaced) loops, you have two closely-overlapping loops in that area.

Is it possible you deleted the wrong faces and those vertices are no longer connected? Either that or there are still some very thin faces there that you missed?

Thanks for all your thoughts guys. You were right, it was a normals issue.

How do I set the thread to solve?

edit your first post>go advanced>prefix