First transgender activists made a splash when men identifying as female invaded the women-only pond on Hampstead Heath.

Now feminists have hit back by attending a men-only swimming session in protest over proposals that would make it easier for people to change gender.

Amy Desir, 30 – one of two women to gain access to the South London pool last Friday – caused particular consternation by wearing just trunks and a pink swimming cap.

Another woman, who would only give her name as Hannah because she is afraid of reprisals from trans activists, told staff at Dulwich Leisure Centre that they had every right to join the session because they ‘identified as male’.

Amy Desir, 30, wore just trunks and a pink swimming cap to attend a men-only swimming session at a south London pool

Both women used the male changing rooms before joining around 20 men in the 25-metre pool. Ms Desir, a mother of two from Luton, said: ‘We are doing it to highlight the ridiculous and dangerous move towards self-identification.

‘We are clearly not men but by saying we are, we were allowed to join in men-only activities.’

Many of the male swimmers tried to ignore the women but one elderly man asked Ms Desir if she realised it was a men-only night.

She said: ‘He asked me if I knew it was men only. I told him I was a man and he said, “Oh really?” It was a very British response. We are not deliberately trying to offend anyone but raise awareness.’

Hannah, 39, a former civil servant, was accompanied by her husband David, 46, an accountant. She said: ‘I’ve never been an activist and I’m incredibly nervous about doing this but the issue prompted me to take action. It is about safety and dignity – people have a right to segregated areas. It is not enough to say I am a man and use male changing rooms or vice versa.’

Hannah emailed the leisure centre in advance to ask what arrangements were in place for a woman who self-identified as male.

Another woman told staff at Dulwich Leisure Centre (pictured) that they had every right to join the session because they ‘identified as male’

General manager Natalie Lane told her: ‘Any customer is free to use the changing room they feel necessary for themselves. We do our best to avoid modern prejudices. However, opinions vary given the diversity of our customer base.

‘If you wish to attend the Friday evening sessions you would do so with the full support of the team.’

In its guidelines for pools, Swim England states: ‘We may need to do some educational work with other centre users who may be concerned when sharing a space with a trans person, especially if the customer... [has] different physical characteristics to the gender they are identifying with ie: a male to female trans customer who has not had top or bottom surgery.’ The campaigners are particularly concerned that Labour is about to confirm it will allow men who self-identify as female to be added to all women shortlists.

Ms Desir has started a petition calling for women to be consulted about the proposed changes to the Gender Recognition Act.

‘We’d like a mass protest at the Hampstead male-only pool, maybe when it gets warmer,’ she said. ‘We’d also like to gain access to one of the men-only clubs in London.’

Bernard Reed, a trustee of the Gender Identity Research and Education Society, said: ‘This case demonstrates that women may enter men’s spaces, just as men may enter women’s spaces.

‘Simplifying the current unduly onerous and degrading process of obtaining a gender recognition certificate will just make life easier for trans people.’