I have been providing advertising and marketing companies and independent agents with private-label high-quality web design and development services since 2003, both alone and as part of a design/development team. I can do the same for you.
I have been the web developer of choice for Green Street Productions since 2003, and have been involved with 38 different Green Street websites and counting. In order to provide a transparent solution, my staff listing includes a greenstreetproduce.com email address. I conduct Green Street business on their behalf using this email address as if I am an employee, rather than a supplier.
Whenever I build websites for ad agencies, I always deal with customers in the same manner. I do not conduct business with customers or other ad agency employees/suppliers unless the agency is directly involved, and I will provide this same service to you.
I do list various sites that I have build on behalf of advertising/management agencies in my portfolio, but only with permission; if you don't want me to link to one of your clients, I will not. However, I do not link directly to the ad agency site; I pass all traffic to a client's site through a private URL that cannot be traced back to me. If a client should happen to find their website in my portfolio, I also clearly state that the site was done on behalf of an agency, and to contact the agency for further business requests.
I offer other services that are ad/marketing agency specific. For more information, Contact me or ask me for a no-obligation quote on your next client project.