United Kingdom, Oct. 22 -- Kevin Federline fears "the clock is ticking" for his ex-wife Britney Spears.

Defending his new memoir against claims that he is trying to profit from her struggles, the 47-year-old DJ, dancer and former reality star spoke out after releasing You Thought You Knew, a tell-all book that makes a series of allegations about his 43-year-old pop star ex's behaviour, including claims she was "drunk as hell" around their children and once appeared at their bedroom door holding a knife.

Britney has dismissed the book as "gaslighting" and accused Kevin of "profiting off my pain," saying on Instagram: "If you really love someone then you don't help them by humiliating them."

Speaking to the Daily Mail, Kevin has now reje...