Those pessimists who believe that political apathy rules in Britain should have paid a visit to Birmingham this weekend. While Labour and the Conservatives agonise over falling membership, one branch of activism is booming.

Hundreds of young women flocked yesterday to the UK Feminista Summer School – slogan: "Organise for a world without sexism". The agenda included the art of creative protest, non-violent direct action and resisting everyday sexism. The two-day event has been sold-out for weeks and, for the opening session, the hall was packed.

Ellie Terry, 26, from Leeds, was not surprised. "The outside perception of feminism is that it is older women, talking about the 70s, but there is a lot more to it and it attracts a young audience," she said. "This is a great time to meet like-minded people and revitalise the movement."

UK feminists have had a good year. The campaign group No More Page Three has taken on the Sun and gained a partial victory. An online petition has attracted more than 114,000 signatures, the support of 140 cross-party MPs and backing from the Girl Guides and the National Union of Teachers. As a result, the Irish Sun has dropped topless images and the editor has employed female executives to look at reinventing the most notorious page in newspapers.

Titles such as Loaded, Nuts and Zoo have come under pressure to obscure explicit pictures of women on their front covers. The Co-operative Group has threatened to ban "lads' mags" from its shelves from 9 September if they refuse to cover up their sexualised front pages.

A new wave of feminist activists and bloggers has flourished online, with social media enabling campaigns to spread their messages and get young people onboard.

Laura Bates, a speaker at the Birmingham conference, founded the Everyday Sexism Project in April 2012. What began as a way for her to talk about her experience of sexism has grown into a global forum. "A guy on the bus was grabbing me and touching my legs. I was on the phone to my mum, and I said this out loud to her and everyone on the bus just looked out of the window," she explained. "Afterwards, what hit me was how normal this was, how it left me thinking, perhaps I should not have worn that outfit, perhaps I had been giving the wrong impression."

A year and a half later, the website has featured more than 40,000 stories from all over the world. "Because so many more women are standing up and talking about these issues it enables other people to stand up too," said Bates. "We can't be silenced any more by people who say you're ugly and bitter and don't have a sense of humour – that's bullying – and the more who add their voices, the harder it is to shout us down."

Inevitably, there was discussion of Caroline Criado-Perez, the feminist campaigner who won her battle with the Bank of England to get a woman on the back of an English banknote, only to be faced with a deluge of tweets threatening death and rape. For those strong enough, there is an emphasis on "shouting back", retweeting and sharing abuse. Others cope by ignoring the trolls and relying on the support of others in the movement. .

One UK Feminista mantra is that sexism is not about men against women but people against prejudice. One in 10 of those attending yesterday were men, reflecting increased male involvement in the last few years. Adam Ramsay, 28, from Oxford, is volunteering over the weekend. He said: "People my age and younger have grown up being told there isn't a problem, and then seen this isn't the case. A lot of men recognise there is a huge injustice in the way the world is run and that you can't ignore it."

The real buzz of the summer school for participants, though, comes from an empowering and energising solidarity among women determined to make a difference. Lucy Holmes, founder of No More Page Three, said: "It's amazing to be here, the support is incredible and everyone is feeling inspired. People are saying to me, 'I love the campaign, my mum loves the campaign'. This is a great way to meet people, and it's always good to brainstorm and get ideas."