Reports in British media this week said Leicester coach Willie Kirk is under investigation by the club amid allegations of a player-coach relationship.
Asked about the need to safeguard players, Hayes told reporters: "Player-coach relationships - they're inappropriate, player-to-player relationships are inappropriate."
Speaking ahead of Friday's Women's Super League clash against Arsenal at Stamford Bridge, the English manager said players and coaches needed to be fully focused "on having the top standards".
Hayes added that player-to-player relationships can make the manager's job more difficult, saying: "One player's in the team, one's not in the team. One might be in the last year of their contract, one might not be. ... We're dealing with human beings. We do talk about it internally."
Ex-Chelsea skipper Magdalena Eriksson and midfielder Pernille Harder, who are a couple, left the London club to join Bayern Munich last year.