Britney Spears’ ex-husband Sam Asghari took a vicious swipe at Kevin Federline over his upcoming tell-all book, calling the dad of six a “professional father.”

In a clip shared by TMZ Saturday , a photographer asked the former personal trainer what he thought of Federline’s upcoming book, which will “detail his marriage with Britney.”

“Well, he was a professional father,” he replied while walking outside West Hollywood hotspot The Abbey on Saturday, cheekily adding that the memoir “would be the first book that’ll tell you how to be a professional father.”

Federline — who was married to Spears, 43, from 2004 to 2007 — announced his upcoming memoir, “You Thought You Knew,” earlier this month.

Per the Daily Mail , the former backup dancer — who shares sons Sean Preston, 19, and Jayden

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