Britney Spears did cocaine while still breastfeeding sons, Kevin Federline claims

Britney Spears allegedly did cocaine while still breastfeeding her two sons, according to a bombshell claim out of Kevin Federline’s memoir.

The Princess of Pop’s ex-husband alleges in “You Thought You Knew” that the incident took place at his “Playing With Fire” album release party in 2006, according to an excerpt obtained by Us Weekly.

Since the “Toxic” singer, 43, had initially said she would be home with their two sons — Sean Preston, now 20, and Jayden, now 19 — Federline was surprised to find her and his father-in-law at the bash.

“I was happy [Jamie Spears] had decided to come support me,” Federline recalls. “He threw a look my way, shook his head and motioned to my dressing room door. His expression sat in that flat blank space between disapproval and apprehension, as if to say: ‘She’s here, and it’s not good.’”

When Federline opened the door, he claims he saw “Britney and [a] young starlet friend snorting a fat line of coke off the table.”

He alleges, “Both were wearing these outrageous wigs. Britney’s was electric blue. It was surreal. They didn’t even try to hide it.”

Federline doesn’t name the other woman in his book — but describes her as an “actress who was about to blow up from a role that would transform her life.”

Britney’s brother, Bryan Spears, and agent Jason Trawick were also in the room during the singer’s alleged drug use, according to Federline.

Sean Preston and Jayden were respectively 1 year and 1 month old at the time, and their parents’ marriage allegedly ended that evening when Federline requested Britney not nurse them.

“A breastfeeding abstinence period of 24 hours has been suggested for women who occasionally use cocaine while breastfeeding,” according to the National Library of Medicine.

Federline remembers saying, “Please don’t go home and breastfeed the kids like this. Call your mom or someone. We need to get formula. You can’t do this.”

Britney allegedly threw a drink in her then-husband’s face, with him telling readers, “That was the proverbial final straw, the breast-feeding thing. Her reaction. That’s what ended us.”

Days after Federline’s lawyer, Mark Vincent Kaplan, sent a legal letter demanding Britney stop breastfeeding the little ones, the Grammy winner initiated divorce proceedings.

“It all happened so fast,” Federline writes, noting that he “couldn’t even catch [his] breath.”

The duo had been married for only two years when Britney filed to dissolve the union in November 2006, and the divorce was finalized in July 2007.

Britney’s rep has yet to respond to Page Six’s request for comment regarding the cocaine allegations — but did hit back at Federline’s memoir’s “sensational” claims on Wednesday.

“With news from Kevin’s book breaking, once again, he and others are profiting off her,” the spokesperson told us. “Sadly, it comes after child support has ended with Kevin.”

As for Britney, she railed against the alleged “white lies” in “You Thought You Knew,” which comes out Oct. 21, via X on Wednesday.

She wrote in part, “The constant gaslighting from [my] ex-husband is extremely hurtful and exhausting.”