freitasm:
I am not aware there's any law that requires you to disclose your current pay. It's actually against your interests in negotiations to tell a possible employer what's your pay now.
Better yet, there's no reason to work for such a company. They are already showing how low they treat employees.
I think that's taking an entirely dim view of the situation. There are scenarios whereby there is no intent to screw a potential employee, in asking the question.