'Should have slapped you in your f***ing face:' Britney hits out at sister Jamie Lynn

Britney Spears has hit out at her sister Jamie Lynn online. Photo / Getty Images

Britney Spears has come out swinging against her sister Jamie Lynn in an explosive new Instagram post.

The singer has hit out at her sister, whose newly-published tell-all memoir Things I Should Have Said about their lives growing up has triggered a public feud between them.

In a new post, Britney recalls how she "flew home to Jamie Lynn on the couch watching her tv shows right after Justin and I broke up ... I was a ghost there".

"Jamie Lynn is 12, she indulges with the TV for hours then goes to lay out on a raft at the pool ... I'm in shock because this was never my life."

She recalls how when reporters from People Magazine turned up her younger sister said she was "scared".

"My Mamma was on pain medication and could barely hold a conversation in the house because her and my dad split and she was more messed up than anything! I remember her sitting on the floor in a conversation and she never got up," Britney continued in her online rant.

"And I'm sorry Jamie Lynn, I wasn't strong enough to do what should have been done ... slapped you and Mamma right across your f***ing faces!"

It's the latest in a string of insults exchanged between the sisters over social media over Jamie Lynn's book, but the younger sibling has since reached out in an effort to end their dispute.

She wrote on Instagram Story: "Britney - just call me, I have attempted many times to speak to you directly and handle this privately like sisters should. But you still choose to do everything on a public platform."

Jamie rubbished Britney's recent suggestions that she's been making false claims about her sister in a bid to sell her new book.

Her post continued: "In the meantime, please stop continuing the narrative that I haven't been there for you or that I'm making things up. I'm happy to share how many times I've reached out to you, supported you and tried to help you. This is embarrassing and has to stop. Love you."

- Additional reporting Bang Showbiz