The journalist-turned-TV presenter will join Susanna Reid in fronting the ITV breakfast programme between 13 and 17 April as cover for Ben Shephard.
He said: "I'm very excited to be joining Susanna and the GMB team for a week. Thanks to my 3-year-old daughter's sleeping pattern, I've been waking up at 4am for quite a while now. So the early starts shouldn't present any problem."
Naughty Piers had got plenty of Twitter followers thinking he may have been replacing Jeremy Clarkson on Top Gear by tweeting: "In ten minutes, I will be announced as the temporary replacement for a very popular TV presenter in the UK.
"No, no, it's 100% true. I really am standing in for a popular male TV presenter on a big UK show. Start filming in 3 weeks.
"I suspect the announcement, at 2pm UK time, will shock, delight & dismay everyone in equal measure. But that's showbiz."
Piers will film Good Morning Britain while working on the new series of Life Stories.
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