Kevin Federline is reportedly planning to write a tell-all book about his life with Britney Spears unless he gets what he wants from their divorce settlement.

According to Star magazine, Kevin isn’t happy with the money he’s set to get from Britney as stipulated in their prenuptial agreement: he’s rumoured to be getting as little as $250,000 in spousal support and a cut as low as 20% from the sale of their Malibu estate.

A source close to Kevin told the magazine: “Kevin is either hoping a publisher will pay him big money for the book or that Britney will cough up more cash than what’s in their prenup to keep him from spilling the beans.”

In addition to money, Kevin wants sole custody of the couple’s two sons, Sean and Jayden and according to the magazine, can “prove that Britney is an unfit mother” with a candid video he shot of Britney just before she filed for divorce.

The source added: “Kevin says he filmed it just a week before Brit filed for divorce. He told me, ‘I want the world to see that Britney is an unfit parent and that she’s not in her right mind.’”