The 33-year-old, due to bring his playing career to an end in the summer, suggested that he is happy to see out the rest of his contract in the stands.
Mertesacker said that he will "finally be free" once he swaps his club captaincy role at Arsenal for a coaching position with the academy, but Hamann claims that the centre-back is setting a bad example to younger players.
"He is still under contract with Arsenal and says that he has no more buck and likes to sit in the stands. He is still paid by the club and has a responsibility," he told Sky Germany. "I find that disrespectful to the fans, his teammates and the coach.
"The club is up to its neck at the moment and then you have one of the captains who sits down and says that he no longer wants to play for the club. Whether he is the right person to give young players values such as identity and loyalty next year, I have my doubts."
Mertesacker has been used 10 times in all competitions this term, most recently playing a full part in the 4-2 FA Cup defeat to Nottingham Forest on January 7.