The NSPCC has said it cut ties with transgender activist Munroe Bergdorf because of Twitter statements she made which breached its safeguarding rules.
The children's charity had appointed Ms Bergdorf as Childline's "first LGBT+ campaigner" - but days after the announcement she was dropped.
Ms Bergdorf accused the NSPCC of giving in to pressure from transphobes.
But the charity said its decision was unrelated to her being transgender and it was an ally of the trans community.
However the NSPCC apologised for the way it ended the relationship with Ms Bergdorf, saying it "shouldn't have cut ties in the way we did".
"We should have been more thoughtful and caring about how we managed our relationship with her at the outset," it added.
The charity said in a statement, released earlier this week, that it had tried to make direct contact with Ms Bergdorf before announcing it was removing her from the campaign, but was unable to do so and the announcement "should have been delayed".
The statement came after more than 150 NSPCC staff wrote a letter in support for Ms Bergdorf to the charity's bosses and trustees, saying they were "deeply disappointed" at how she had been treated.
'She deserved better'
In the statement, charity chief executive Peter Wanless said: "We have let Munroe down in not supporting her through a process with us and in ending the relationship abruptly.
"It was our decision not hers and she deserved better from us."
On the reason why Ms Bergdorf was dropped, Mr Wanless said: "The board decided an ongoing relationship with Munroe was inappropriate because of her statements on the public record, which we felt would mean that she was in breach of our own risk assessments and undermine what we are here to do."
The statements - which it said were specific to safeguarding and equality - are understood to have been made on Twitter, when Ms Bergdorf had previously messaged young people directly offering them to contact to her for support.
Mr Wanless said it was a "lack of process that our organisation used when deciding to work with Munroe" which led to the decision to drop her.
Ms Bergdorf is seen as a leading figure within the LGBT+ community and transgender activism, but outside of these communities she has continually divided opinion, at times being forced to step down from opportunities following a social media backlash.
In 2017 she was sacked from her role as a model for cosmetics company L'Oreal, following claims she wrote that "all white people" are racist in a Facebook post.
Ms Bergdorf later said her comments had been taken out of context but said that she stood by her view that "all white people benefit from racism, with white privilege".
The NSPCC said it decided to run the LGBTQ+ Childline campaign after figures show it handled more than 6,000 contacts from children with concerns about their sexuality or gender in the last year.
"We wanted to show our commitment and relevance as a trusted source of support for children and young people with these concerns by running a three-month campaign," the charity said.
When she was announced as a campaigner, Ms Bergdorf had said she was "excited to have the opportunity to let more kids know that they are not alone in how they feel".
But after Ms Bergdorf's appointment was announced, a number of negative tweets followed.
After being dropped, Ms Bergdorf said she was "unbelievably sad", and her spokesperson accused the charity of "bowing down to pressure from a transphobic lobby running a hate campaign".