Bras that pump up or down with body temperature and smooth out ageing cleavages are among hot new undies to be unveiled at this month''''s Paris lingerie show, organizers said on Thursday.

    A Dutch-designed anti-wrinkle bra that can iron out crinkly cleavages as a woman sleeps, and a smart Slovenian brassiere whose foam cups expand with body heat when the wearer works out or flirts, are amid innovations at the January 23-25 Paris trade fair.

   "High-tech''''s playing a growing role in underwear," said the fair''''s fashion manager Sophie Morin. "Take ultra-sounds for example, now used as well as laser technology to cut and construct garments without seaming or stitching."

    Also touted is a range of French lingerie called Milkshake in a fabric made of milk proteins that contains 10 amino acids to hydrate the skin.

   "The knit is as soft as satin," said Morin.

   The cupless anti-wrinkle bra designed by Decollete is supposed to be thrown on at bedtime keeping breasts apart to prevent the formation of feared crinkles that appear in the night.

   "I dread to think of my husband''''s likely reaction if I was to come to bed wearing it," said one blogger on www.truthinaging.com, a site that has already consigned the bra to its "department of daft."

   The smart bra from Slovenia''''s Lisca boasts cups made of memory foam that ebbs and flows with body-heat -- a NASA patented technology from the 1960s.

   Some 20,000 lingerie types from more than 100 nations are due to attend the end-month Paris fair, bringing together more than 500 brands, including Brazil''''s LZ, flying in with an ultra-light bra that weighs in at 67 grammes (two ounces).