
is the UK's biggest lingerie retailer, with a 26% share, but Tesco has been boosting its ranges in an attempt to get a bigger slice.
The Diamond Boutique range launched in March and claims that it sells a luxury silk bra that would normally retail at £40 for £14.
The move comes as M&S prepares to announce its second quarter figures on Wednesday. It is expected to announce a 1.4% fall in like-for-like sales over the quarter.