The arbitrator appointed by the government to negotiate a new contract between Canada Post and its union has stepped down.

Labour Minister Lisa Raitt appointed Judge Coulter Arthur Anthony Osborne as the arbitrator in the case following controversial back-to-work legislation.

The Canadian Union of Postal Workers challenged Osborne because he is unilingual and doesn’t have a labour relations background.

Last month, the union won a stay of proceedings in the arbitration. The Federal Court ruling meant they couldn’t start the arbitration until after the court heard the union’s case against Osborne in January 2012.