In an interview with the Daily Mirror, Emma Marriott, 25, from London, said: "It always shocks me how angry people get about extended breastfeeding."
Emma was speaking out after Time magazine caused an outcry with its cover shot of Jamie Lynne Grumet breastfeeding her son, who is almost four.
Emma still breastfeeds her own four year-old, Haron, but said she never planned it that way.
"I thought the image on the cover of Time magazine last week was beautiful and, as Jamie Lynne is so young and pretty, it really challenges the stereotype that all women who breastfeed for a long time are weirdo earth mother types," she said.
"I never meant to breastfeed for this long. "Throughout my pregnancy, I imagined myself doing it for around a year.
"But I was lucky Haron took to the breast easily and feeding was no problem.
"We both enjoyed it and before I knew it, the first year had flown by and his second birthday was fast approaching.
"So I decided that perhaps we could carry on feeding until he was two-and-a-half - and this quickly became three.
"Now, I find myself breastfeeding a four-year-old... and it feels completely natural."
She said some people express surprise and even disgust when she tells people she is still breastfeeding her son, but Emma shrugs it off.
"I think all the angry and horrified responses are because we have such a weird attitude towards breastfeeding in Britain.," she said.
"My friends living in other European countries such as Holland and Germany aren't nearly as surprised.
The reactions that I struggle with most are the ones from other mothers, who can be really hostile. Some seem to feel a need to justify why they stopped breastfeeding at a much earlier age or didn't breastfeed at all.
"It makes me feel really sad that mums feel this pressure. I don't judge anyone about any of their parenting choices."
So how long will she continue to breastfeed Haron?
"My plan is to let Haron self-wean - in other words, give up when he chooses," said Emma.
"One health advisor recently warned me that he may never stop on his own. But biology won't let him carry on forever.
"Once his adult teeth come in, the shape of his jaw will change, and he won't be able to feed effectively.
"He will be forced to wean at this point, but at least he'll be at an age where we can discuss it."
How long did you breastfeed for?
Do you think there is a natural weaning time?