In her new role she will continue to lead McCallum Layton's qualitative team while taking up a more strategic position at board level.
Horlov joined the agency in 2001 having come from a professional services and manufacturing background with a range of commercial experience. She has a BA in social sciences and a postgraduate diploma in psychology.
Duncan McCallum, founding partner of McCallum Layton, said: "Julia's promotion to partner is testament to the great contribution that she has made to our business.
"Also, it demonstrates our commitment to promoting excellence within our agency so as to provide a strategic approach to delivering research solutions that result in real business improvement for our clients."
McCallum Layton launched in 1982 and now lists its core service areas as: consumer research, B2B research, global research, public sector research, healthcare research and staff consultation. Its clients include Norwich Union, McCain, Littlewoods, Asda, RBS and EDF Energy.