The Strictly Come Dancing presenter marked the incredible achievement by sharing two sweet photos on Instagram.
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"And to think this one just passed her driving test, how time flies! Congrats Phoebe," she captioned the post.
The first picture shows Tess and Vernon holding on to their then-newborn daughter, who is sleeping on Vernon's lap.
Tess shared an adorable photo of Phoebe as a baby
The second photo shows the incredible cake the proud parents treated their daughter to on Wednesday. The strawberry gateau cake has the word "congrats" written on it as well as a cake topper that reads "Congratulations Phoebe".
Friends and fans went wild for the update and rushed to congratulate the teenager.
"Well done Phoebe!" wrote Lisa Dawson, whilst co-presenter Claudia Winkleman added several love hearts.
A fan added: "Congratulations Phoebe, Tess you have a designated driver now," whilst another remarked: "Tess you haven't changed one bit!! Forever young xx."
The couple celebrated her big achievement with a cake
A third wrote: "You both looked so happy there. I hope that that happiness has lasted and continues to do so. Now the days of being concerned start."
Tess and Vernon married in 2003 and later renewed their vows in France five years ago. The couple share two daughters, 17-year-old Phoebe and Amber, 13.
Phoebe's big milestone comes just weeks after Amber celebrated her 13th birthday. To mark the occasion, Tess shared a gorgeous throwback photo of her as a little girl.
Amber's blonde hair, huge hazel eyes and wide smile, even as a youngster, demonstrate the uncanny resemblance she shares with her mother. Tess wrote: "A big Happy Birthday to our beautiful Amber - officially a teenager today."
Within an hour of posting the rare image, thousands of fans, including This Morning's Josie Gibson, rushed to wish the teenager a happy birthday. Nobody could resist commenting on just how cute Amber looked, with one fan raving: "Aww soo cute hope amber has an amazing day," while other fans couldn't believe how time has flown, with another adding: "Happy birthday where do the years go! Enjoy the celebrations."