Kate Middleton fears the Royal family can't handle another scandal

Kate Middleton is hoping sister Pippa Middleton doesn't embarrass her during her first solo tour in the US to promote her new book Celebrate.

The Duchess of Cambridge,30, is terrified Pippa might say something damaging about her or the Royal family.

But Pippa, 29, is less than keen at being ordered around by her big sister.

'It's causing real ructions,' reveals our source.

'Pippa thinks Kate's not being supportive.

'Let's not forget that Pippa's her own person and not on the Palace payroll.

'Meanwhile, Kate's in doubt over whether she can trust her sister to not let her down.'

The Duchess is feeling anxious after she was left humiliated when topless pictures emerged on 13 September of her on holiday in France that were published in French magazine Closer.

And while Kate's determined to make sure things go smoothly for her little sis, insiders fear Her Royal Hotness could be targeted by paparazzi desperate to capture her unawares in her down time.

'The Palace want Pippa to turn down all party invitations, but she sees them as an essential part of her promotional obligations and is insisting on attending,' says the source.

'The Duchess is also concerned that Pippa will be tricked into talking about if the Royal couple are trying for a baby and Kate's weight issues.

'She's even enlisted the help of their parents, Michael and Carole Middleton, to pressure Pippa to think carefully about what she will or won't say in interviews.'

Read more about Kate Middleton andPippa Middleton in Now magazine dated 15 October 2012- out now!

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