A British baroness, ex-model and former head of a lingerie empire has expressed her embarrassment after the "child" she lifted into her arms for a photo turned out to be a 46-year-old married man.

Michelle Mone, 44, was attending an entrepreneurs' conference in Vietnam when the man approached her bearing a bouquet of flowers, The Mail on Sunday reports.

The 44-year-old stooped down to accept the gift and picked up the man, assuming he was a child.

"Only realised when a woman shouted with laughter 'that's my husband'," the baroness wrote on Twitter.

"Everyone thought it was hilarious, including him."

Baroness Mone said the man was fine with the incident but said she did have a slight suspicion he was older than she first thought after picking him up.

The pair smile for a photo. (Twitter)