Thanks for the replies.
I have tried cleaning the wipers with kitchen roll and it didn't really help. I also have to top up the windscreen washer container about every 3 weeks. The smearing is annoying when there is only light rain.
I think Nick hit the spot with his post.
RainX sounds good too, I'll try that.
Cleaning the wipers alone would no help. You need to do the lot that was advised. Including looking at nicks rivet thing. If someone has put washing up liquid in the screen resorvoir it may never get better. You may find with rainx you still need to decontaminate your screen. Anybody know about applying it? Don't want the chap wasting his money.