Cream carpet always gets dirty by skirting boards

[Whoever]

We have cream carpeting throughout and I've noticed that immediately at the base of all the skirting boards a dirty black line appears where the carpet tucks into the floor. I vacuum weekly and damp-wipe the dust off the skirting boards so does anybody know how I can remove these dirty lines and prevent them from reappearing? 1001 carpet cleaner doesn't appear to really clean them up.

[lajohn]

cut off the dirty black line.

[buildersmate]

As per cleversod, but the explanation is due to the generous amount of vauuming you are doing. Because of this gap, grubby dusty air is being sucked through the bottom of the skirting board into your carpet when you put the sucker into the corner like this.