It's unlikely the car parking area forms part of the leased premises. Therefore, the Centre Management can make rules about the use of their 'common' areas, and how they can be used. If they refuse you permission to park in a particular area which is part of their property, then you can't park there.
They cannot, however, threaten your employment. They don't have that power. The power they do have, however, if the lease is appropriately worded, is to issue a notice of breach of the lease to your employer - who will likely take action against you pretty quickly for fear of incurring costs or being kicked out of the lease