Campaigners have called for discussion of transgender rights to focus on respect, generosity and the elimination of prejudice after the prime minister stated that “basic facts of biology remain overwhelmingly important”.

At Wednesday’s PMQs, Boris Johnson told MPs that “we must recognise when people want to make a transition in their lives that they should be treated with the maximum possible generosity and respect” but added “when it comes to distinguishing between man and woman, the basic facts of biology remain overwhelmingly important”.

Johnson was responding to a question from Angela Richardson about the interim report of the Cass Review into gender identity services for young people in England and Wales, which raised serious concerns about the lack of data collection on outcomes for the recent increase in young females questioning their gender identity.

On Tuesday, the UK government announced that it was planning a comprehensive cross-government strategy to “advance” the rights of the LGBT+ community, covering healthcare, sex work, veterans and homelessness.

Johnson’s remarks, which reference the argument that sex-based rights should not be eroded by those based on gender identity, stand in contrast to those of the Labour leader, Keir Starmer, who recently stated that “trans women are women”. When asked to define a woman in a recent interview with The Times, Starmer replied: “A woman is a female adult, and in addition to that trans women are women, and that is not just my view – that is actually the law.”

Responding to Johnson’s remarks, a spokesperson for Stonewall said: “Trans people currently find themselves the subject of much debate, but what is evident and inarguable is that trans people exist. And their existence shows us that human lives and experiences cannot always be sorted into neat little boxes.

“We know that most people share our goal of a world where everyone is safe and free to be ourselves. Supporting lesbian, gay, bi, trans and queer people to live freely and fulfil our potential means tackling the prejudices and stereotypes that hold so many more people back.”

Kai O’Doherty, head of policy and research at Mermaids, the charity supporting transgender youth, said that Johnson’s remarks should not be taken out of context.

“We were pleased to see the PM’s answer today included an important emphasis on ensuring we treat trans people with respect and generosity and that his latter comments were distinctly made within this context. We believe it is in everyone’s interest to not attach so much weight to biology when discussing trans matters. Sex rights and trans rights are not at odds with one another.”

Groups campaigning for women’s sex-based rights welcomed Johnson’s remarks. Fair Play For Women described it as a “clear commonsense answer” while Lesbian Labour tweeted “whilst the Tories remain better on this issue Labour will not win an election”.

Finn Mackay, the sociologist and author of Female Masculinities and the Gender Wars, argues that while biology is important, so are laws to recognise and protect identities. “Also there’s the issue that our biology, if he means genitals and reproductive systems, aren’t visible most of the time. So biology isn’t always the most useful; I’m called ‘young man’ regularly, I’m not young or male.”