The new business will include three strands: UP Consultancy, which will offer corporate and leadership communications advice to big businesses; UPstart PR, which is aimed at the UK's growing start-up scene; and Inside UP, which will advise on internal comms.
The latter is the province of Lynne Arrowsmith, who is EE's head of internal brand and comms.
The pair are leaving EE at the end of the month having each worked for the company and its predecessor, which merged with T-Mobile in 2010 to form EE, for more than ten years.
Stuart Jackson was director of comms at both Orange and EE, also handling corporate affairs at the latter, before changing in 2012 to work directly for chief executive Olaf Swantee in a wider business-focused role, titled director, CEO office.
Swantee said: "It has been a pleasure working closely with Stuart. He is a hugely talented communications professional with an ability to mix both the creative and corporate skills needed to deliver success. He goes with our very best wishes and we will watch the progress of his new venture with great interest."
Arrowsmith was praised by chief of corporate and strategy Stephen Harris as "one of the creative founders of the EE brand, having developed the culture, values and internal identity of what has become Britain’s biggest communications company".
EE is planning to appoint replacements for both Jackson and Arrowsmith, whose departures follow the retirement of chief of brand and comms Steven Day in late 2013.
The company’s other senior communicators are director of corporate and financial affairs Dan Perlet and director of corporate comms and PR Mat Sears, who both report to Harris.
Jackson said: "During my time at the company I have been incredibly fortunate to work with, and learn from, some of the finest business leaders around.
"Being part of the senior team that successfully merged two of Britain’s biggest companies before being given the opportunity to create a new business and a new brand, has been a truly incredible experience. I am extremely proud of what we've achieved and my thanks go to Olaf, the EE team and the many colleagues I've worked with over the years."