The attached article is a fairly detailed analysis of what constitutes Joint Employment.
A very broad definition of joint employment is that (as the name implies), an employee is controlled by two different companies and thereby is legally employed by both. The question is who owns the liability?
Each agency is different, however if you do business with Sqrft we make it quite clear that since you fully control our referred’s environment and activities, and since we are not on your job site directing them in any way, you are responsible essentially to the extent that you would be if you hired him off the street.
One variation of this might be harassment. I recognize that although I cannot control your employee (who may have done the harassing), I can control my response and ability to intervene on the referreds behalf. Our policy on this is that we would bring the complaint to management of your company and expect you to handle it properly and expeditiously. If that doesn’t happen then one remedy that we can provide is to remove the employee from your environment and offer him work at another company (to the extent that we have it available).
At any rate, the following link provides a good analysis of what your liability might be —> Joint Employment and the Contingent Worker – Are Your Temp Agency Workers Really Your Employees?