Harwood-Matthews, previously chief executive of BDH\TBWA, takes on the same role at TBWA\Manchester, in partnership with Fergus McCallum, formerly chief executive of Tequila\Manchester, as chief operating officer.
As part of the move, all TBWA's Manchester agencies, including Tequila\Manchester and interactive agency Digerati, will come together under one company, with a shared management team and bottom line. The group agencies will retain their current names in the new structure.
Harwood-Matthews said: "This signals a huge step change for us. Fergus and I share the same vision of delivering fresh, media-neutral ideas to our clients, our shared philosophy is that you cannot outperform a market if you adhere to its conventions."
Mick Foden, previously creative partner at JWT London, has been named executive creative director of the new TBWA\Manchester.
Foden, who famously penned the Conservative Party tagline "Are you thinking what we're thinking?", will work in tandem with Richard Sharp, the agency's existing executive creative director.
Other appointments include Lorna Hawtin as "disruption" director, with Liz Ingham and Karen Hall becoming operations directors.
Alexandra Johnson has been appointed network director and Steve McCarron will take on the newly created role of head of media arts. McCarron will launch a new planning approach, pioneered by the LA-based Apple account team.
Harwood-Matthews said: "We have the talent and the tools to challenge the old establishment order and deliver smarter, more creative and better executed solutions for our clients."
BDH's clients include Nissan Motor Great Britain, Best Companies, Wickes, AG Barr and Brother.