A friend asked me tonight if I could tell him what is wrong with his potatos. They have little worm like holes in them and when cut open there are several branches of tunnels. Is this because the soil is not clean enough and if so what should he do for next year please? Any help would be much appreciated.

it could be possible that they've first suffered from blight, then been eaten by slugs

did the leaves have black spots on them?

http://www.rhs.org.uk/advice/profiles0902/potato_holes.asp

Or could just have been slugs, regardless of whether they had blight. What variety were they? Some are more slug resistant than others.

Thanks for the suggestions. My friend is unsure of the variety but says there were no leaf black spots. The first ones to be lifted were OK only the later ones have the holes and apparently little worms in some of them.

Wireworm? Check out the following to see if it was these:

http://topveg.com/2008/03/08/wireworms-in-potatoes/

I suffered with wireworm my first year (the ground hadn't been worked for a couple of years)

Do you know what the variety is Baz ?

Thanks to you all for the help. The wireworm description fits to a T.