The 50-year-old, who fronts ITV1's This Morning, was forced to release a statement about her secret after hearing that it was about to be exposed by the News of the World.
Viewers have seen Fern shed five stone in the past two years. She had told fans that her dramatic weight loss was the result of exercise and healthy eating.
Fern's agent John Rush initially denied the gastric band claims yesterday, telling the News of the World: "This story is preposterous and utterly untrue. If you publish it, it is a libellous statement."
However, in a statement issued hours later, Britton said: "As I know, many people are interested in my weight loss over the past two years. As interest is so high I'm making public, as a personal choice, that I had a gastric band operation two years ago. I did this purely for myself and I would not wish to influence others to do the same. But for me it has worked and I am very pleased with the results."
Fern had previously denied suggestions that she had taken the easy way out when trying to lose weight. In an interview with Now magazine, she said: "I've always said I'm not a fan of dieting, so I just ate a bit healthier and took up cycling to work. I've heard a rumour that another celeb has been saying I've had liposuction. That's hilarious! It's taken me two years and a lot of hard work. I can wear my bikini with pride."
A spokesman for ITV has said that the network will be standing by Fern and rejected claims that she had misled This Morning viewers.
"We weren't aware of this matter - over the last two years Fern has cycled down the Nile, she exercises most days and has a very healthy lifestyle and healthy diet," he said. "As far as we're concerned, she lives and breathes what she talks about."
He added: "This is not a con."