Day, who joined Burson-Marsteller in 2014 as managing director of the agency’s public affairs and political communications practice, was then made chief operating officer in January 2016, becoming second-in-command of the UK business.
The agency said that, under Day’s leadership, its public affairs team and revenues had seen "significant growth" and referred to his inclusion in the PRWeek UK Power Book among the reasons for his promotion to the top UK job.
Ramiro Prudencio, chief executive of Burson Marsteller’s EMEA region, said: "I am very excited to have Stephen assume responsibility for our UK operations. As head of our public affairs practice, and later COO, he has led our teams to pursue innovative, creative and data-driven solutions to client challenges. This experience will be essential to continuing the transformation of our UK business as we seek to lead in integrated communications spanning all practice and industry areas."
Prudencio added that Day’s background in public affairs would be of particular value to the agency’s clients as the UK prepares to leave the EU and that he would join Burson Marsteller’s regional leadership team.
Prudencio was appointed to his role in April as part of a major senior management re-structure at Burson-Marsteller. The changes at the top of the WPP agency began with the promotion of Kevin Bell to worldwide president in December 2016.
Before joining Burson-Marsteller, Day spent four years running Portcullis Public Affairs as managing director. He has also worked for both FleishmanHillard and Weber Shandwick. Day started his career in 2000 working for the Conservative Party’s Front Bench Trade and Industry Team.
Bell said: "Stephen is an inspiring leader who is highly regarded by clients and colleagues alike for his strategic thinking, foresight and rigorous attention to excellence."
Bell also paid tribute Pierce, who took on the role of UK chief executive four years ago, taking over from former Labour Party general secretary Matt Carter.
He said: "Amanda Pierce recently left the role of CEO to embrace her next big challenge. She has been a collaborative, innovative and results driven leader, achieving a great deal in the last nine years. I have always had admiration for her ability to get stuff done, and I would like to thank her for the considerable contribution she has made and wish her all the best for the future."
From day one, working closely with Ramiro and the team, I will seek to look anew at our approach to communications to innovate and grow both in terms of people and capability so that we always live up to the needs and expectations of our clients and people alike.Stephen Day, newly appointed chief executive of Burson-Marsteller's UK operations
Day said said: "From day one, working closely with Ramiro and the team, I will seek to look anew at our approach to communications to innovate and grow both in terms of people and capability so that we always live up to the needs and expectations of our clients and people alike.
"Burson-Marsteller in London will reflect the city in which we are based by being truly global facing, dynamic, entrepreneurial, diverse and, above all, successful."
The new agency chief has been listed as one of the UK’s top ten political communicators in PRWeek’s Powerbook for the last two years.