Today, Brighton city centre is going to be hit by a breastfeeding flashmob. After being verbally attacked for not covering up while feeding my four-month-old, I decided it was time to make a statement to show that mothers will no longer tolerate being harassed for feeding our babies in public.

Mothers are protected as part of the Sex Discrimination Act 1975, but also by the Equality Act passed in October 2010, where it specifically states it is unlawful to treat a woman differently because she is breastfeeding. However, I was sitting breastfeeding in a cafe recently when a woman approached me to tell me how unpleasant it had been to watch me. She said she could see "everything". I had layered my clothing, so as to make a discreet pocket to pull out my breast and feed, so I struggled to see how she was offended. I defended myself and the discussion escalated into a row with the people she was with. The only man in the group of five forcefully told me, "You should have used a towel, most women use a towel." The group left and I calmed down but my upset turned to anger.

This wasn't the only incident I had come across. Other mums have been telling me about how they experienced similar humiliation. An online poll conducted by Mother & Baby magazine in 2009, involving 1,200 mothers, revealed that 60% felt the UK frowned upon public feeding. I've had enough of our society's bizarre attitude to the female body.

The Brighton event won't be the first of its kind in the UK; women in both London and Manchester staged flashmobs for National Breastfeeding Awareness week in June. But it is part of a growing trend.

Flashmobs are reminiscent of "Happening" art performances in the 1960s but on a much larger scale. They usually involve doing something not associated with traditional forms of protest, such as synchronised dancing or freezing still like statues. Perhaps this lighthearted style of protest in large numbers makes us feel safe enough to bring out our inner rebels.

But increasingly, flashmobs are being used to make political points. The United Cabbie Group has arranged a couple of vehicle flashmobs in London to protest against the ban on taxis using the Olympic bus lane. Their intention was to raise awareness of how integral the mode of transport was to London, not to disrupt traffic, so after 45 minutes they dispersed and went back to work.

There was also a flashmob in Trafalgar square in November to raise awareness of the brutal regime in Syria. A group of people lay down on the floor and draped a flag over themselves without saying a word. Similar events were synchronised for the same cause in Canada and Austria.

The flashmob modus operandi fits perfectly with breastfeeding. A large group of mums feeding together creates an extraordinary sight. It's the most obvious way to show support, sitting side by side feeding our children.

I considered letting the harassment incident pass unmentioned. But I have two daughters, and if they in future choose to have kids and breastfeed, I don't want them to feel self-concious or to be victimised. I have been overwhelmed with comments from mothers thanking me for taking a stand. We may well be viewed as militant mums and that is certainly the essence of a thread already started about me on Mumsnet. But I'm hoping our flashmob will also bring a smile to people's faces, and we will no doubt have a giggle.

• The flashmob will take place on Thursday 15 December at 1pm at the Clocktower, Brighton