The couple have been married for 12 years, after they tied the knot at Lake Como in Italy in 2012.
Confirming her news via an Instagram Story, Love Actually actress McCutcheon has said that the pair have decided it is best for them to go their separate ways.
In her post, McCutcheon stated that their main priority is the "happiness and welfare" of their nine-year-old son, Rafferty, and they "look forward to being parents together" for the rest of their lives.
"After much thought and consideration, Jack has decided it's best for us to separate after 18 years together and I accept his decision", McCutcheon wrote. "We are both so very blessed and grateful for our beautiful, nine-year-old son Rafferty, whose happiness and welfare has always been, and will continue to be, our number one priority".
"We both of course still cherish and look forward to being parents together to our wonderful boy for the rest of our lives".
McCutcheon continued: "Our love for Rafferty is something that will never waver or change and we obviously want to protect him and help him feel as safe and secure as possible".
Asking for privacy at this "difficult time", Martine McCutcheon also said that their split had evolved over time, and they are still "finding our new way forward as a family".
The actress also sent McManus "all the love, luck and happiness for the next chapter of his life". She also added that she will be "rooting" for him alongside their son.
Thanking her followers for their support, McCutcheon signed off by writing: "Thank you all for the love and support, now and always… Martine xx".
As well as starring as Natalie, the lovable assistant to Prime Minister Hugh Grant in Love Actually, Martin McCutcheon had previously been renowned for her role as Tiffany Mitchell in BBC soap EastEnders.
