Wallace married teacher Heidi Brown, who is 17 years his junior, in January 2011 after meeting her on Twitter.
"Due to a number of factors Gregg and Heidi have made the difficult and mutual decision to take some time apart. They remain on amicable terms with only the best support for each other," a spokeswoman confirmed.
The food expert has apparently moved into a bachelor pad, while Brown, who works as his personal assistant, looks after his two children from his second marriage in their former marital home.
"Gregg and Heidi are so sad they haven't been able to make their marriage work. But they've drifted apart. Gregg has just thrown his weight into his work. They realised a few weeks ago that it wasn't working and decided to split up," a source told the Sunday Mirror.
"He's been busy juggling his catering business and his showbiz career. All these things together have taken their toll. But they're determined to stay extremely close, with Gregg visiting every weekend. She is also still working as his PA, managing his diary and updating his website, so they speak all the time."
Wallace's first wife Christine left him after just six weeks of marriage in 1991, while second wife Denise left in 2004 after five years of marriage when she discovered he had been cheating on her.