Provided that the haulms do not have blight then it is quite OK to compost them. Make sure that you have removed all the small potatoes first or they will grow.
If they have bligh then they should be put in the bin for the dump or burned on a hot fire.

I've just been told off for the above answer :-(((
I believe that it is OK to compost healthy haulms but all of ours go into the council bin. This is because there is so much of it and the compost bins are getting full by the end of summer.

I prefer the better safe than sorry route :-)