Pippa Middleton will not be able to promote her forthcoming book because it could "embarrass" her sister.
Duchess Catherine's younger sibling is soon to release her party planning bible 'Celebrate', but publishers are concerned they are in a "tricky situation" because of her close ties to the British royal family.
A source said: "She would normally be expected to appear on every chat show under the sun.
"I know she won't do anything that she hasn't run by the duchess' advisers, but it is still a very tricky situation."
Despite being offered the chance to have the tome ghost-written, Pippa - who rose to fame as her sister's maid of honour at her April 2011 wedding to Prince William - has insisted on writing it herself.
The source added to the Mail on Sunday newspaper: "She was offered a whole host of ghost writers but said no to them all and is very proud that it is all her own work.
"I just don't think she appreciated how much work it would take and may need some help from her editors."