The Victoria's Secret star said: "My one piece of advice for buying lingerie for someone else would be to have a sneaky peek in their underwear drawer to get an idea of their size and style.
"Nothing causes more tears than lingerie bought two sizes too small - or two sizes too large for that matter!"
Whiteley has been designing an underwear collection for Marks and Spencer since 2012, and recently launched her spring/summer 2014 offering.
According to Vogue, she said of the latest range: "We continued using sumptuous silks and French designed lace, but we also evolved the prints and shapes in keeping with the mood of the season and whatever inspires me when we designed the collection.
"For spring, we also have the second collection of sleepwear, featuring silk pyjamas and the softest jersey loungewear."
The British beauty also opened up about this year's Valentine's plans with her boyfriend, actor Jason Statham.
She said: "This year I will be spending it at home with my boyfriend, over a delicious home cooked meal and a glass of wine."