I work for a charity and they have decided to replace part of my hours with a volunteer. They will be cutting my hours (and pay) by 36%. This will then make it possible for them to cut my benefits. Does this constitute constructive dismissal and do I have the right to ask for a severance package instead of the new, reduced position?

Unless you have a contract that gives your employer the explicit authority to reduce your hours and salary, the employer cannot unilaterally do so and if they proceed to without your consent it is a clear constructive dismissal. Please contact us at the number below for a consultation with a lawyer to discuss your employment situation.