Assigning an employee's voluntary duties on a permanent basis

Is it a fundamental change of employment if employee is already doing the work?
By Brian Kenny
|Canadian Employment Law Today|Last Updated: 05/27/2015

Question: If an employee voluntarily takes on different duties from her regular job and then the employer decides it wants the employee to do those duties permanently, can the employee claim constructive dismissal if she wants to go back to her old job but the employer refuses?