Lewtas, who has 23 years' experience in the ad industry, replaces Richard Sharp, who left TBWA\Manchester at the end of last month to pursue other interests.
The appointment marks Lewtas's return to the TBWA fold -- he was creative director at TBWA\ Chiat\Day, New York between 1999 and 2001 -- and is the first major hiring made by recently promoted chief executive Fergus McCallum.
In Manchester, he will take charge of the agency's creative department and oversee client brands including EA, Nissan, BP, COI, PZ Cussons and The Co-operative.
Lewtas has spent the past five years as a creative consultant, which has seen him fill roles such as acting executive creative director of IPG's Team Nokia in New York and working at Saatchi & Saatchi on its European client Toyota.
McCallum, who was promoted from chief operating officer at the end of last year, said: "We're delighted Pete has agreed to join us and he already has fantastic knowledge of the network and its core philosophies.
"Combined with his depth of experience across a wide range of global brands and creative disciplines, he is absolutely the right person with the right passion and insight to head up the creative team at TBWA\ Manchester and help drive the agency into its next phase of development."
Prior to his stint as a consultant, Lewtas was the creative director of Amsterdam-based Fuel, where he worked with clients including Volvo.
Lewtas said: "TBWA\Manchester has a lot of talent, a fantastic list of clients and a great deal of untapped potential.
"It's in an ideal position for us to deliver more for clients by building on this creative strength."
Lewtas cut his advertising teeth in 1986 when he started working at Gold Greenlees Trott as a copywriter.
He moved to BMP DDB in 1990, before embarking on a career as a commercials director and freelance writer.
He has won numerous awards including golds at the British Television Advertising Awards and Cannes, and a silver D&AD.