The 42-year-old - who plays mature student Mike Barnes - finished filming with the Channel 4 soap at the end of last year and will remain on screen until January 27 when he bids farewell to the village for pastures new.
Speaking exclusively to DS about his decision to quit, Hirst said: "I've been there four years, I've had a great time, I love the place and I love the people dearly - but I need to freshen up. I need a new challenge, I need to play different characters, and it would be very easy for me to stay there for a long period of time and I don't think that would be any good to anybody.
He continued: "It also fitted in with the timing of the storyline of Sarah's death and Kathy being continually sectioned and Amy growing up. It would be difficult for them to shoehorn [any more] storylines in for Mike."
Hirst first appeared in the soap in January 2006 and has over the year been involved in some of the soap's biggest storylines due to the trials and tribulations of his screen wife Kathy and daughters Amy (Ashley Slanina Davies) and Sarah (Loui Batley), who recently died in a tragic parachuting incident.
Plots have included Amy's pregnancy, Kathy's obsession with Amy's baby Leah and a romance with Sarah's best friend Zoe (Zoë Lister).
Off screen, Hirst is due to co-produce a play with ex-EastEnders actor Chris Coghill - Tony King in the Walford soap - based on the Strangeways riots.
> Click here to read our full interview with Tony Hirst in Soap Scoop