Employer not approving the annual leaves, what can I do?

I had informed a month prior to my scheduled annual leaves of 1 week. But my HOD is continuously refusing to provide approval on the leaves even though I have requested him many times. Even though they are continuously saying that year end is a critical time to provide leaves when the leaves are required to be availed but he has all the required personnel to manage the work in my absence. But he is rejecting the leaves request blindly saying no leave shall not be given to any employee during that time. He has been playing politics along with his subordinates and making a performance issue against me for the past few months even when there is no performance issue. They are specially targeting me & trying to spoil my image in view of sacking my job. Now when I already have done the reservation for the trip, being a female do I have a strong case against the harassment done to me by my employer due to the issues so far and also due to this leave issue if I go for leaves without approval.