Postal ballots and hidden intentions

The first comrade I bumped into after getting back from holiday late Saturday told me very apologetically he had junked the Labour Party mailout, which included the NEC ballot paper. The envelope design is telling. By coincidence another set of ballot papers arrived this morning from Unite. Which body really wants its member to vote? Shouldn't there be a code to govern the conduct of postal ballots by political parties? A new role for the Electoral Commission, perhaps.