Kevin Federline Says Britney Spears Was Drinking, on Meds While Pregnant

Kevin Federline claims Britney Spears was seriously "Toxic" ... literally, for her children.

K-Fed alleges the Grammy-winner drank alcohol while pregnant and on medication in an excerpt from his book, "You Thought You Knew," obtained by People.

Kevin writes, "That mix was... dangerous. F----d up, honestly ... You’re not supposed to drink when you’re on meds like that. A couple of glasses of wine for her would hit like a whole bottle because of the medication.”

This comes despite Spears writing in her 2023 memoir, "The Woman In Me," she "never" had a drinking problem or "any interest in hard drugs."

K-Fed writes otherwise ... “I had seen it before, her drinking and breastfeeding, and it was really upsetting because of the danger to the kids ... She could have pumped milk for Jayden so her mom had that ready.”

The exes have two children together, Sean Preston and Jayden James.

We previously reported Kevin also claimed Britney did cocaine while she was still in the breastfeeding phase.

Britney's reps gave us a statement Tuesday ... "With news from Kevin’s book breaking, once again he and others are profiting off her and sadly it comes after child support has ended with Kevin. All she cares about are her kids, Sean Preston and Jayden James, and their well-being during this sensationalism. She detailed her journey in her memoir.”