Mr Cameron was asked if he had one of the popular all-in-one leisure suits after Mr Clegg admitted being given one during a radio phone-in last week.
Speaking on ITV's Daybreak, Mr Cameron said he had not joined in with the trend, which has seen grown men and women wearing the romper outfits.
He said: "My children have onesies. I often say that I'm very jealous that they didn't get me one."
Last week Mr Clegg told London's LBC 97.3 radio that he had been given a "big green onesie" in Sheffield but said he had not worn it and it was still in its packaging.