Concerns have been raised that a proposal to have issues such as abortion and homosexuality enshrined on the school curriculum will be used to "indoctrinate" children with sexual ethics that their parents may object to.

The Scottish Parliament has taken forward a petition by sex education lobbyist Sexpression:UK calling on MSPs to take the near unprecedented step of using the law to compel schools to provide sex and relationship education (SRE).

Discussions about domestic violence, rape, assault and child abuse should be compulsory from a young age, Sexpression:UK spokeswoman Rebecca Ryce told Holyrood's Public Petitions Committee.

Children could be asked to imagine the difficulties they would face if they brought home a same-sex partner or discuss whether abortion is appropriate, she added.

Conservative MSP Jackson Carlaw raised concerns that a child who objected to the statutory "received wisdom" would be told that they are wrong.

The Free Church of Scotland said such a regime would be "an absolute breach of human rights".

Mr Carlaw said: "My concern is that when it become part of the statutory curriculum there is a received wisdom as to what is correct.

"I have already seen with my own son's education, in a completely alternate example, where they were talking about the political systems and my son argued that he thought first-past-the-post was the correct political system, and he was marked down because that was incorrect.

"He was told the ideal political system was a proportional one. That struck me as a perception of somebody else's truth being imposed on him.

"Now, I extend that to sexual education and sexual attitudes, and I would worry that there was a received wisdom as to what was correct and that anyone who perhaps took an alternative view to that would be told that they are wrong, when in fact that is a subjective argument and not, in fact, an absolute one."

Ms Ryce said the curriculum would be split into factual information about issues such as sexually-transmitted infections and the effectiveness of contraception, and discussion points on subjective topics.

"I do not think that teachers should be told to preach any sort of ideology at all - it should be more about facilitating discussion," she said.

"I think it's good for children to hear all sides of the argument as I think that will inform their learning.

"For example, with gender-based violence I think that should be compulsory.

"Discussions about domestic violence, rape, assault and child abuse should definitely be brought up in schools from a young age.

"There are core values that I think we should be promoting, certainly, but never an ideology.

"For example, abortion is always the one that is the big controversy and I think that it can definitely be taught appropriately.

"You put the information out there and you give them scenarios and say: is it appropriate? What would the religious view be?

"It's never about preaching, it would be more about asking others to facilitate discussion on these topics and it would never be an exam.

"You would never get two marks for mentioning a certain study. It would be more like RE where you have a discussion."

She added: "LGBT is not done enough. I think a lot of homophobia stems from misunderstanding.

"It's about clarifying terminology for children and just letting them know things like: HIV is not a gay disease. It's surprising how many people still think that and still associate that with the gay community, and particularly gay men.

"Then there is the more discussion-based lessons. Lesson plans that we do around homophobia can be things like setting up scenarios where you imagine yourself bringing your opposite sex partner to dinner, and then imagine if your partner was the same sex and what kind of issues that would cause you."

Scotland has almost no statutory curriculum, with only religious education and Gaelic instruction in certain regions enshrined in law.

The school curriculum is established through guidance issued by Education Scotland, rather than being set out in statute, and the Scottish Government notes that responsibility for sex and relationship education lies primarily with local authorities.

Commenting after the committee, Free Church of Scotland leading minister Rev David Robertson said: "On the surface Sexpression's concerns seem justified and their solutions reasonable.

"However, in reality it is a trojan horse which will be used to indoctrinate our children into the particular sexual ethics and philosophy which Sexpression regard as right.

"In their absolutist beliefs they will not allow differences of opinion and instead they insist that every child should be indoctrinated into their philosophy - a philosophy which has continually proved itself unable to prevent sexual harm, disease and disaster.

"We would regard it as an absolute breach of human rights for children to be 'educated' in a particular sexual philosophy, which is contrary to the wishes of their parents and ultimately harmful to the child."

The committee agreed to take forward the petition and seek further advice from the Scottish Government health and education departments, and look at international best-practice on SRE.