TORONTO -- Progressive Conservative Leader Patrick Brown said Monday that he used to oppose the Liberals' sex-ed curriculum, but did not address a revelation that he had promised a social conservative supporter he would repeal it.

Brown issued a statement late Monday night saying he was against the changes to the curriculum when they were first announced, calling them "undeniably controversial."

He does not identify which changes he felt were controversial, but said the premier did not adequately explain them to parents.

"I have since come to the conclusion that significant opposition to the curriculum was rooted in a refusal to accept LGBT elements into the curriculum," he wrote.

"Concerns were exaggerated and have not borne out. I've met with many educators, parents and school boards -- some of whom opposed the curriculum -- and they are satisfied with how it's been implemented."

The new curriculum included updates such as warnings about online bullying and sexting, but protesters have taken issue with discussions of same-sex marriage, masturbation and gender identity.

Brown's statement follows the publication of a 2015 email in which he says he would scrap the curriculum -- a position he denied last week that he had ever taken.

"I will repeal it!" Brown wrote during the party's 2015 leadership race in an email to Jack Fonseca, with Campaign Life Coalition. "I say that everywhere."

Brown wrote that then-leadership opponent Christine Elliott "thinks I am wrong for the party given mine and (MPP Monte McNaughton's) opposition to sex education."

Fonseca said he also heard Brown make the promise to repeal out loud to others.

"Indeed he did say that everywhere when he spoke to groups and individuals and social conservative leaders," Fonseca said. "He told them all he would repeal it."

When asked last week when his views on sex ed changed, Brown said he has always taken a "middle of the road" approach, criticizing the government for not consulting parents enough, but not on the need for the curriculum.

Brown has said he was livid to discover that a letter was distributed under his name in a recent byelection promising to "scrap" the curriculum. Brown said it did not reflect his views and he did not see the letter before it went out.

But emails from his chief of staff appear to suggest the Progressive Conservative leader was aware of the promise.

Brown has said the local byelection campaign office had gone "too far" in writing that he would scrap the curriculum.

But emails obtained by The Canadian Press show Brown's chief of staff, Nicolas Pappalardo, distributed the letter the day before it became public.

And in an email from the week before Brown said he became aware of the letter, Pappalardo wrote that Brown himself "was prepared" to make a statement saying, "If elected, a PC Government would introduce a new curriculum after thoughtful and full consultation with parents."

By backtracking on his promise to scrap the Liberals' sex-ed curriculum, Brown has betrayed social conservatives, Fonseca said.

"He's a politician ... who doesn't stand for much at all -- it's whatever the political winds lead him to believe will bring him more power or help him maintain power," he said.

Brown said he is "sorry" Fonseca and his group are upset, but he is "running to lead all Ontarians."

"If the price to be paid is that my political opponents will say I've 'flip-flopped,' so be it," Brown wrote. "If you want a rigid ideologue as premier, vote for someone else."

A coalition of groups that oppose the curriculum is planning a rally at the legislature Wednesday, with MP Brad Trost, who has said he will run for leadership of the federal Conservative party, as one of several "special guest speakers."