Two typical phrases for refusing permission in a gentle way are:

• I'd rather you didn't.
• I'd prefer you not to.

These phrases can be used after either Do you mind if...? or Is it OK / all right if...?. They are usually followed by some sort of explanation or alternative suggestion.

1. Do you mind if I turn the stereo on?
2. I'd rather you didn't. You see, I have to finish this report by 7 o'clock.

1. Is it all right if I go home early?
2. Erm... I'd rather you didn't, if you don't mind. We've got one or two small jobs to finish.

We could also answer in the following way: Yes, but... (for Is it all right if...?) or No, but... (for Do you mind if...?).

1. Do you mind if I turn the stereo on?
2. No, but could you wait until I've finished this report. I won't be much longer.

1. Is it all right if I smoke?
2. Yes, it's all right, but do you think you could smoke in the other room? You see, I have a bit of an allergy to tobacco smoke.