Should I wash my recycling?

I tend to wash my recycling because I was under the impression that dirty recycling couldn’t be used. My husband always said it didn’t matter as they wash it at the recycling centre anyway. The council (who collect the bins) are silent on the matter. Other people we know who live in a warmer climate say that their instructions are not to wash, just scrape out any food residue. I tend to want to clean it, since it might be hanging about for up to 2 week before collection. Does the washing negate the environmental benefits of recycling?