Wardle, who is 18 years old, made two substitute appearances for the club last season and has progressed through the Bulls Scholarship and Academy system.
Bulls Head of Youth Development Paul Medley said: “Whilst it is always disappointing when a young player decides to take up an offer from another club, we offered Joe a big increase on his current contract, an offer we felt was commensurate with both his ability as a player and his potential over the next three years. Unfortunately he has chosen to further his career elsewhere and to that end we wish him all the best.
“However, we are only interested in players who want to play for the Bradford Bulls and fortunately we have a lot of those who are desperate to play for the club and make their career at the Grattan Stadium, Odsal.”
Any Super League club signing Wardle will have to pay the Bulls compensation in accordance with RFL Compensation Rules.