Rob Kardashian has signed a tell-all book deal.

The sock designer has appeared estranged from his famous family in recent months and plans to lift the lid on how they have been ''tainted'' by fame, with particular venom reserved for sister Kim Kardashian West and her husband Kanye West.

A source said: ''Rob was approached to do a tell-all book and he's recently signed a deal.

''He plans to claim that Kim sometimes uses her daughter North to promote Kanye West's tour and that her marriage is partly based on money and publicity.

''He wants to show how fame has changed and tainted the family over the years.

''They were a traditional church-going family who were very close and put each other's welfare first, but now he says they often row and everyone's falling apart in their own way.''

Kim was said to be so furious when she heard the news, she is even considering legal action against her brother.

The source added to Closer magazine: ''His mum Kris Jenner isn't managing his career so he was able to sign the deal without her knowledge.

''He's on the warpath with Kim and is telling everyone he's going to lay her secrets bare. Kim was livid when she found out - she's even discussed legal action if he writes anything negative about her.''