Stop in government wasting £billions per year with current budget

Every year uk government departments waste billions of pounds in march to spend their full budget entitlement before April when they do not need the money. They do this because if the money is not spent they get less entitlement next year. I have worked in small teams that have wasted £70000 in march on stationary that they will never use. Wouldn't it make more sense to hand back any underspend and have the option to request more if you ever need it? The small team I mention above will go on to waste this money year on year for no reason...stop this atrocity!