The Big Bloomers Company was set up by mother and daughter Dianne and Laura Mannering earlier this year offering underwear up to XXXXXXXXL for 35-stone women.
But they have been inundated with calls from obese women around the world complaining they are too SMALL.
Dianne and Laura have now produced a style at a gigantic XXXXXXXXXXXXXXXL to fit 45-stone women who have a 8.75ft waistline and a dress size of 74.
They went on sale last week and have already proved to be a huge hit with around 100 customers snapping them up.
Dianne, 68, said the "super-super size" range was proving popular in New Zealand, Australia and France.
She said: "We realised there was a woeful lack of selection and so decided to cater for much larger women, which proved very popular.
"But I have to admit I was very surprised when I started getting phone calls asking for even bigger ones.
"We ship them around the world and, at the moment, New Zealand and Australia are the biggest takers.
"Our customers have been very enthusiastic and have given us help to tweak the design and make the knickers more accommodating."
Dianne, a retired insurance broker, set up in business in Penryn, Cornwall, with Laura, 46, in April after spotting the gap in the market.
Within weeks they were being contacted by customers begging them to make larger garments.
The company also sells tights and big-size gowns, which can use up to six metres of fabric.