My employer has given my hours to someone else can they do that?

I work as the cook for the local pub only in the daytime as it is only when they serve food, in the evening I work there as a barmaid for the past month i have taken on the cleaning doing 2 hours each day five days a week my boss has now taken these off me leaving me nearly �80 each week lighter in the pocket he has offered these hours to someone else who is not employed there I have tried to approach him and ask why he has cut the hours he just shrugs his shoulders and can't give me a reason he is now giving me the cold shoulder and making it clear he expects me to leave altogether can someone please help