The Spaniard weighed in on the club versus country debate amid calls for England's top young players to represent the Under-21s at next summer's European Championships.
"It's a debate that comes up every two years and that shows that it needs clarity," The Mirror quotes Martinez as saying. "It's unfair on the players because they're put in a position where they feel that they have done something wrong.
"It doesn't help. It ends up with someone being the bad guy - be it the player, the Under-21s manager or the club. I don't get it.
"It's a debate that needs to be talked through and then it has to be put in a way in which this is what we are doing, that's it; no matter who the player is once they get into the senior squad they don't go back so that everyone knows where they are."
Barkley is in line to make his return when Everton take on Aston Villa in the Premier League this weekend.