The smaller charity has accused CRUK's current 'I shouldn't be here' campaign of diverting awareness and resources away from cancer- specific charities by using case studies of people talking about the kind of cancer they had, including bowel cancer.
Neil Brookes said: "It's like Tesco moving into a neighbourhood and squashing smaller retailers. Because of its power and size, CRUK can do what it likes. Unfortunately, it doesn't understand or chooses to ignore the consequences of its actions on organisations such as ours."
Bowel Cancer UK is now writing to Professor Alex Markham, the chief executive of CRUK, to propose a meeting to discuss ways of working together.
A spokeswoman for CRUK said: "We have successfully worked in partnership with other charities for many years. We fund more than £217m worth of research each year, including £14m on bowel cancer."