As you probably already know, if you ask prospective employers not to contact your former employer, you raise a red flag. A company considering hiring you will probably call your boss anyway, since they don't actually need your permission to call. It is not illegal for an employer to give out truthful information or opinions about your work. Do not assume that your employer is prohibited by law from giving more than "name, rank and serial number." So, before you completely cut your ties with your employer, find out what your company would say about you to prospective employers. Then try discussing what information you do or do not want released. You may also try writing a generic "to whom it may concern" reference letter about yourself and then asking your employer or supervisor to sign it or use part of it in their own letter. Be prepared to push for a good letter and also be prepared to discuss changes in the exact wording of the letter. A positive letter of reference can go a long way toward improving your employment future. In a unionized workplace, if an employer declines to assure you a positive reference, consult your union to explore the possibility of filing a grievance.