Boris Johnson has waded into the trans rights row, saying "biological males" should not take part in women's sport and venues should have women-only spaces.
The Prime Minister said that was "as far as my thinking has developed" on trans rights and "seems to me to be sensible", though he acknowledged he may be "in conflict with some others".
He was speaking at a hospital in Hertfordshire on Wednesday after more than 100 organisations pulled out of a major LGBT conference - Safe To Be Me, planned for June - in protest over his failure to include trans conversion therapy in a government ban on the practices.
The PM said he was "sad about the reaction", which came after a partial U-turn in which the government banned all gay conversion therapy,
But he refused to back down, adding he believed women-only spaces should be protected and "biological males" should be excluded from women's sport.
He added he was "very proud" of his record on LGBT issues but "complexities and sensitivities" remain around the ban.
The PM said: "When I became Foreign Secretary, I insisted that the LGBT flag should fly over embassies in other parts of the world where they didn't necessarily share our values. So I'm 100% committed to this.
"And we will have a a ban on on gay conversion therapy, which to me is utterly abhorrent. But there is there are complexities and sensitivities. When you move from the area of sexuality to the question of gender, and I'm afraid there are things that I think still need to be to be worked out.
"I'm sorry, we haven't been able to, to reach agreement with with the organisation's concerned but that that will in no way diminish our determination to tackle prejudice wherever we can."
"Let me just say, because this is something that you know, frankly, for people like me, it wasn't something I thought that I would have to consider in great detail."
Labour leader Keir Starmer, meanwhile, has accused the Government of "distraction tactics" and "flip flopping". He said Labour would ban conversion therapy "in all its forms".
The PM said some of the issues are "novel concepts", but went on to volunteer "a few points".
He said one issue was whether younger teenagers could be considered Gillick competent - a legal term referring to whether a child under 16 can consent to medical treatment without the need for parental guidance.
It comes after transgender cyclist Emily Bridges was barred from competing in a women's event after the sport governing body ruled she was not eligible.
Bridges, 21, began hormone therapy last year to reduce her testosterone levels.
New guidance from the Equality and Human Rights Commission also clarified this week that transgender people can be legitimately excluded from single-sex services - but only if the reasons are "justifiable and proportionate".
The watchdog said that the justification could be for reasons of privacy, decency, to prevent trauma or to ensure health and safety.
The PM said: "I don't think that it's reasonable for kids to be deemed so-called Gillick competent, to take decisions about their gender or irreversible treatments they may have. I think there should be parental involvement at the very least. That's the first thing.
"Secondly, I don't think that biological males should be competing in females sporting events. Maybe that's a controversial thing to say but it just seems to me to be sensible.
"And I also happen to think that women should have spaces, whether it's in hospital or prisons or change rooms, or wherever, which are dedicated to women.
"That's as far as my thinking has developed on this on this issue. And if that puts me in conflict with some others, then we got to work it all out.
"That doesn't mean that I'm not immensely sympathetic to people who want to change gender, to transition. And it's vital that we give people the maximum possible love and support in making those decisions, but these are complex issues and I don't think they can be solved with one swift, easy piece of legislation. It takes a lot of thought to get this right."
Mr Starmer said on a BBC Radio 5 Live interview that Labour would ban all conversion therapy.
He said: "That used to be the Government's position but they have been flip flopping on this over the last few days.
"They need to stick to their promises. But I can't help feeling that this is yet more distraction tactics from the Government.
"They know that what is keeping people awake at night is the cost of living, whether they can pay their bills or not.
"In order to try and distract from that, the Government wants to create an argument about conversion therapy. It's not going to wash."
