Oh, I expect what will happen is you'll give your boss's details to the recruitment agent, who will phone him before you've handed in your notice and then pester him about finding a replacement for you. You'll return to work to find a boss who is furious that:1. You're looking for a new job2. You didn't tell him3. Some random recruiter is now hounding him with sales calls on the phoneThen, when you don't get offered the new job for whatever reason (not least because of the lack of a glowing reference), you'll be up the proverbial creek without a paddle. So, lesson of the day - don't let the agent take up the references!