Bates paid the price for a disappointing season at Kingston Park which brought just six victories and saw the club narrowly avoid relegation from the Premiership.
Coach Alan Tait was subsequently appointed head coach but then revealed the club will not be directly replacing Bates in a director role following a backroom reshuffle.
Tait said: “There will be no director of rugby coming in, and I as head coach will be in charge of the rugby department. I am the man in charge of the rugby side of the club. I will decide which players come, which players leave and which players get selected in the team each week.”
Meanwhile, Wasps have completed the signing of scrum-half Nic Berry from Racing Metro 92.
Berry, an Australian under-21 international, brings with him a wealth of experience from the French Top 14 and Super12/14 competitions. He said: “The chance to discover a new city and a very competitive Premiership was too good to turn down.”