A psychologist who has played a key role in opposing the introduction of relationship and sex education lessons in schools is being investigated by her profession’s governing body over her fitness to practise.

Dr Kate Godfrey-Faussett, who has extensive experience working with young children and families, is a leading figure in Stop RSE, a campaign against relationship and sex education (RSE) lessons in schools.

In a speech broadcast online, Godfrey-Faussett, who converted to Islam 25 years ago, has that said many young Muslims were “turning to same-sex relationships because they haven’t had the guidance”. She has complained about the “queering” of the “Muslim community” and said Muslims should “work psychologically or in a mental health capacity” with those experiencing same-sex attraction.

Parliament last week voted in favour of the lessons by a huge majority: 538 MPs backed the proposal, brought by education secretary Damian Hinds, which will mean children are taught about different family models from primary school. It is the first time relationship education guidance has been changed since 2000. Pupils will be taught about same-sex couples and parents, lesbian, gay, bisexual and transgender identities and about the dangers of stereotyping such groups.

The vote came after a sustained campaign against the lessons, which initially centred on several schools in Birmingham but later reportedly spread to Manchester, Oldham, Blackburn and Bradford. Parkfield community school in Birmingham found itself at the forefront of the row after protests by predominantly Muslim parents against its No Outsiders programme, which taught children about LGBT identities. Some Muslim parents said that the lessons went against their religious beliefs.

The National Secular Society (NSS) wrote to the Health and Care Professions Council, which regulates Godfrey-Faussett, to ask whether her views on homosexuality were compatible with its standards.

In a letter dated 18 February, seen by the Observer, the society warned the council that the Stop RSE campaign had “promoted material which says the punishment for homosexuality is death. Our research has found that downloadable resources which were available on Stop RSE’s website as recently as last week [since withdrawn] included a book which endorses lashing and killing gay people.” It is understood that the council accepts that the society’s concerns fall within its remit. As a result, it has launched an inquiry, gathering relevant information and judging it against the council’s conduct, performance and ethics standards.

According to the council, if a registrant’s fitness to practise is considered impaired, “it means there are concerns about their conduct, competence, health or character which are serious enough to suggest that the registrant is unfit or unsafe to practise without restriction, or at all”.

A spokesman for the council told the Observer: “We are aware of concerns about Kate Godfrey-Faussett and are looking into what action, if any, we need to take. We have a duty of confidentiality to all parties involved and it would not be appropriate for us to comment further.” Godfrey-Faussett said she had not been informed of the details of the complaint to the council, other than that it had been made by the NSS.

“I have simply tried to warn people of the underlying liberal secular agenda of RSE and the harm that it may cause children – and is, in fact, already causing based on reports I am receiving from parents,” she told the Observer. “It is well known that if you speak out against the secular narrative they will silence you through smear campaigns and getting you struck off professionally.”

NSS chief executive Stephen Evans said efforts to prevent teaching about LGBT people were well coordinated and rooted in bigotry. “Those behind them are undermining legitimate, age-appropriate education which introduces children to issues and people they will inevitably encounter in a healthy, pluralistic society,” he said. “The demand to impose religious conservatism on state schools is unreasonable and must be resisted.”