I'm a PhD student and one of my research assistants (undergraduate student) applied for a non-research volunteer position on campus. He asked (via email) for me to be one of his references on the day of the application deadline. I didn't see the email until the day after. In my reply email, I apologized for not catching the email in time, said it would have been better if they gave me more than a few hours warning, and that hopefully he was able to find another letter writer in time.
He replied and said that he had put my name down as a reference anyway because of the deadline. I'm not sure if this was due to them misunderstanding how references work (first job?), or cultural differences (international student?), or procrastination with the application and simply assumed I would be OK with it. In his followup emails he seems to be aware that this was an inappropriate thing to do, but had no choice due to the deadline.
The problem is that even if he had asked me earlier I would have declined to be a reference anyway, primarily because I don't know the student well enough to write a positive letter (he had only been working in the lab for a couple of months at that point).
Today, I received the request for my reference letter, asking me to rate the student on various qualities and some open ended questions. I have enough time to write the letter, but I'm not sure of the correct course of action.
On the one hand I wouldn't have written an overly positive letter in the first place and putting me down as a reference without my permission worsens my impression of the student. But on the other hand I feel that as a supervisor (of his lab work anyway) I should suck it up and help them get the job regardless of how I feel about this situation, as he has been a fairly good student (kind and friendly) in the lab for the little time that I've known him. Additionally, I'll still be supervising the student in the lab regardless of whether he gets the job, and writing a bad letter may sour the relationship and create unwanted tension in the lab.
I'm not sure how to handle this situation. Should the employer be made aware of what happened? Can/should I decline to write the letter? Would there be any negative repercussions for me if I decline to write the letter after being put down as a reference?
I see that there is already a question on here about declining to write a reference (Should I decline to fill out a recommendation form after saying that I will do it?), but in this case I never agreed to write the letter in the first place and this was all done without my permission (or awareness, until after the fact).