Parkus has been in the position on an interim basis since Daglish departed in June. He will manage the 150-strong team in the UK and focus on client leadership, commercial growth, talent management and new business.
He also joins Havas Media Group’s senior management team and play a role in helping to "steer the group strategy".
Having joined the agency last year as managing partner, Parkus has worked on the Royal Mail, Domino’s and Westfield accounts, and helped the shop win Savills, Uber and Universal Music.
Parkus will report to Paul Frampton, group chief executive at Havas Media Group UK and Ireland, until Arena has appointed a chief executive to replace Pedro Avery, who was promoted to global CEO of Havas Sports & Entertainment Cake last December.
Before joining Arena, Parkus worked at The Specialist Works as UK group director of planning. His career also spans ZenithOptimedia and Starcom MediaVest.