Sarah Brown is also writing a blog on her time at the G20 summit
Sarah Brown's followers on the social networking website Twitter now appear to be outstripping those of popular celebrity "tweeter" Stephen Fry.
The PM's wife now has more than 774,000 followers on the website Twitter, compared with about 768,000 for Fry.
Her popularity on Twitter far outstrips that of the official Labour Party feed which has about 6,000 followers.
Mrs Brown is currently updating followers on her experiences as a "G20 spouse" at the summit in Pittsburgh.
She also uses Twitter to promote her charity campaign for better maternal healthcare in developing countries.
Writing under the name SarahBrown10, the PM's wife has sent out 1,162 messages since joining Twitter in March.
She tends to steer clear of political statements, instead giving followers a glimpse into the practicalities of her day-to-day life.
Recently she has described visiting London Fashion Week, attending a "gorgeous" wedding and watching Britain's Got Talent winners Diversity dance at Downing Street.
Sarah Brown attended an event to highlight maternal mortality this week
During the performance the group's youngest member fell, but Mrs Brown reassured Twitter fans: "Lovely concern for Perri from Diversity and have checked: he is fine and has done 12 flips today."
Each so-called "tweet" is limited to 140 characters and her latest described having dinner at the G20 in the "lovely environment" of an organic farm.
Mrs Brown is also writing a blog from G20 in which she talks about catching up with Michelle Obama and looking forward to some "exciting trips" that the First Lady has planned for the "G20 spouses".
The PM's wife has been increasing her public profile and in recent months has been photographed alongside supermodels and Hollywood stars at events like Glastonbury and London's Gay Pride parade.
Last year, she introduced her husband's keynote speech at the Labour conference in Brighton - a move that even he said "surprised" him.
She is also a campaigner for women's rights and fronts the Million Mums campaign for better pre- and ante-natal care in the developing world.