The 35-year-old presenter was at an incident at 10 Downing Street hosted by Prime Minister David Cameron and his spouse Samantha.
During a trip to the ladies, the zip on the back of Holly’s dress up against it and left her posterior exposed to the world.
Speaking about the incident on the ITV breakfast slate today, she told viewers: “I went to the loo, stood up and then I heard this excursions and the zip on the back of my dress went completely.
“Now this isn’t just a little zip, this zip repudiates from top to bottom. So I am now stood there with no coat, no phone in the john in Downing Street on my own, thinking ‘what do I do? I can’t walk out, my bum is out.’
“I can’t walk out, I had to wait for someone to finish in the money b be in.”
Holly revealed that eventually a woman came in and fetched her conceal. When he found out what had happened he told most of the people he met and the help.
She said that the Downing Staff offered to use gaffer tape to put her reprove back together and even use safety pins.
In the end though, Holly done up the night wearing her winter coat over the dress to hide her awful wardrobe malfunction.
The Celebrity Juice star also admitted that she had to foretell the PM’s wife what had happened when the ir posed for a photograph together, who yelled with surprise.
“Everyone’s wearing normal clothes and I was wearing this grievous big winter coat!” Holly squealed.
Her co-star Phillip Schofield could contrariwise laugh at the funny story.
This Morning is on ITV1 on weekdays at 10.30am.