I'm contacted by a recruiter and she asks for references. I don't want her to take reference at my current employer, as I don't want to undermine my further job opportunities there. They need explicit permission in writing to contact references but, I know, sometimes they still do. How can I explicitly but politely ask the recruiter not to take reference at my current employer? I just can't come up with a good, clear sentence.
It would be extremely unlikely and unprofessional for a recruiter to do this, however you can say something like this if you are concerned:
Do not contact my current employer for references as this will jeopardise my job which would be very detrimental to both my career and personal situation. Please ask me for explicit permission before doing so.
You are trying to impress on them that they are risking your job security.
Most recruiters are asking for references for one reason - contact building. It has nothing to do with you, your job or any potential job. All they're concerned about is getting another name and number of a (what they presume is) a hiring manager in their database. Plus, they know that they'll be looking soon, when you leave..!
My advice is to simply advise that references will be available upon a job offer being made.
There's absolutely no need to provide references prior to this point. Be aware that many recruiters will lie through their teeth to tell you otherwise - excuses such as
We need to check your references before we put you forward. or
The client demands references up front for all applicants. but you need to hold firm.
As you've already discovered, the recruitment industry is not a hotbed of ethics and the only safe approach is to guard information.