Is your current employer aware that you plan to leave?

Here the interviewer wants to know that you are being straight with your current employer. They could also be giving you a chance to explain any negative aspect of your current employment. In some cases they may have already got some idea. Normally a company would not approach referees without specific permission. So there is a need to ensure that your answer demonstrates respect and proper behaviour. This does not mean that you have to tell your current employer anything but do indicate that you will give the proper notice and not let them down.