Cheaper French wines are often best avoided but when it comes to spending around �20 there are very few countries which produce wines as good as the French can.
I'm sure your father would love a good quality claret but, because the French never make things easy for us, the one word which you won't see on a bottle of claret is 'claret' ;-) Instead, look for the region 'St Emilion' (which produces some superb clarets), together with the words 'Grand Cru' (which defines the wine as being of the highest quality).
Warpig3 suggests Chateauneuf-du-pape. While I agree that you'll get a decent wine if you buy a bottle, my opinion is that it's often over-priced relative to its quality.
Kleiber suggests a Spanish Rioja Reserva. I love Rioja (as, I'm sure, will your father) but, at �20 per bottle, you should be looking above the 'Reserva' level of quality. The label should state 'Rioja Gran Reserva'.
Chris