Kenton has claimed that Princess Diana accepted posters of models wearing lingerie and swimwear for Prince William and Prince Harry to display in their school dorms.
The lingerie company is now forbidden to display the royal coat of arms and has been stripped of its royal warrant.
Kenton also described carrying out bra-fittings with the Queen, stating that royal was half-dressed and her famous corgis were present at the time.
The 82-year-old bra-fitter wrote: 'I never met William or Harry - though [Princess Diana] was always talking about them. I gave her posters of models in lingerie and swimwear for them to put up in their studies at Eton.'
'Diana had an amazing figure. She ordered a few swimsuits by Gottex, the Israeli designer, and some cover-ups and beach bags to match,' she added.