The 37-year-old focused on a bikini snap of her “mega babe” parent, which saw her posing in just a white two-piece.
Unlike Holly Willoughby, she sported lengthy brunette tresses while her incredible figure was impossible to miss in the skimpy swimwear.
Flashing a cheeky smile at the camera, the presenter’s mum was seen with her arms across her chest in a plunging top, which featured cut-out detailing in the middle.
Her toned tum took centre-stage in matching briefs, while she sported smokey eyes and wavy locks.
“Total and utter mega babe… then and now!” Holly captioned it.
She continued: “My Mumma… 70 today! Love you beyond… Happy Birthday beautiful.”
Holly went on to upload two of her mum as a child and another of her posing alongside a male.
The beauty also included a selfie of herself with the birthday girl, as they beamed at the camera.
The mother-of-three was quickly inundated with replies to her post, with many saying how much the pair looked alike.
Two commented: “Family of babes!! Good genes,” and: “@hollywilloughby can see the resemblance.”
“Can see where you get your looks from holly, happy birthday to your mum,” a third agreed online.
Another exclaimed: “Mega babe????? She could have been a Bond Girl. What a stunner!!! Good genes @hollywilloughby.”(sic)
Many others simply gushed about how “simply stunning” the photos were, with one reading: “A very happy birthday! Very Bond Girl in that white bikini.”
Holly also took time to revealed her latest This Morning ensemble with her devoted followers.
Standing in front of a brick wall, she teamed a pair of black culottes with an animal prin shirt and towering heels.
“Morning Thursday… today’s look on @thismorning… trousers @majeofficiel shirt @jcrew shoes @very #hwstyle,” she revealed.
It comes just days after Holly was slammed for wearing her wedding dress as she watched Meghan Markle and Prince Harry’s royal wedding last weekend.
She took a trip down memory lane as she dressed in her floor-length frock from her 2007 nuptials to Dan Baldwin, which came complete with lace detailing.
Her first upload saw her posing alongside her sister and mum in their respective wedding dresses, who were also celebrating milestone birthdays.