The blonde beauty was left red-faced by the fashion mishap in a throwback clip from an episode which aired in 2013.
She had opted to wear a chic grey shift dress with a jewelled neckline for the Channel 4 programme but it failed to stay closed.
When she turned to the whiteboard to solve a calculation, she revealed that the back of her frock had popped open.
The awkward malfunction left what appeared to be her lingerie on full display for those watching the show at home.
Her silky slip dress could be seen underneath the tight-fitting number, which highlighted her peachy derriere.
Rachel, 31, seemed completely unfazed by the fashion mishap as she professionally continued to co-host the show.
It’s not the only time that she has suffered a wardrobe malfunction on the show.
Just last month, eagle-eyed viewers noticed that her skintight blue dress had split at the back.
One viewer commented: “What’s going on with the back of Rachel’s dress?!”
As another noted: “Wardrobe malfunction for Rachel Riley or her dress is one size too small for her.”
Despite the gaping hole at the back of her frock, the bright number showcased her toned pins as she accessorised with a pair of silver stilettos.
Countdown airs weekdays on Channel 4 at 2.10pm.
Daily Express :: TV and Radio Feed
