The answer to this question will depend on state law and will vary, perhaps widely, from state to state. It will depend on if and how your state defines "full" and "part" time, and what the related regulations may be. Generally there is little legal definition, and companies may define "part-time" and "full-time" in a number of ways. You'll want to read your employee handbook carefully, and then consult with your state employment division. However, I think you'll find there is no legal requirement to designate part-time employees as full time regardless of the number of hours they work. (At one time in California, I was working 60 hour weeks as a "part time temporary" employee. However, that was many years ago, and the laws may have changed.) RJTRIES: If you read my answer carefully, you'll see that I indicated that there was probably no such requirement, so I don't understand why you rated my answer poorly. I answered the question that was asked, correctly, even according to your comment. Please make sure you've read and understand the answer before you rate it. Also, the last part of your comment is unintelligible and seems to be trying to answer a question that wasn't asked, which weakens the impact of your rating.

Generally speaking---No. Some labor contracts do specify that if a part time worker works in the same job for over 40 hours for a given period (like 6 months), then that demonstrates the need for the employee to create a full time position; but that doesn't mean that the specific part time employee who worked it will be assigned to it. The contract usually specifies that the senior part time employee will be assigned to it or the position will go up for "bid."