The Church of England will be asked to denounce gay conversion, consider special services for transgender people and re-examine its teaching on marriage as between one man and one women in a raft of measures to be debated at its forthcoming General Synod meeting in July.

In its first meeting since the surprise rejection of a bishops' report recommending keeping the status quo on marriage, the CofE's parliament will debate whether to join medical experts and condemn so-called 'gay cures' as 'unethical, harmful' and having 'no place in the modern world'.

Tabled by senior synod member Jayne Ozanne, the private members motion has received strong support from synod members. Supporters say that it is likely to be fiercely opposed by a small segment of hardline conservatives, but opponents suggest that many middle of the road synod members will also be alarmed by the motion.

Ozanne, a gay rights activist on synod, told Christian Today: 'It is incredibly important that religious organisations follow the clear lead set by the health care professions in standing against this highly damaging and unethical practice, which reinforces stigma and prejudice against the LGBTI community.

'The Bible teaches that we are each fearfully and wonderfully made, and we should therefore look to celebrate God's gift of diversity in creation not treat those of us who are non-heterosexual as having mental disorders that need to be "cured".'

If passed, the CofE would co-sign a statement from several professional bodies including the UK Council for Psychotherapy and The Royal College of General Practitioners to say: 'Sexual orientations and gender identities are not mental health disorders, although exclusion, stigma and prejudice may precipitate mental health issues for any person subjected to these abuses.'

The move would be a major symbolic step for the CofE after the Archbishop of Canterbury called on Christians to 'repent' for 'hurt and pain' the Church has inflicted on gay people.

It may also put pressure on the government to ban gay cure therapies after the Prime Minister hinted she was looking into whether to outlaw the practice.

'Being gay or trans is not an illness, and shouldn't be treated as such – young people should be protected from attempts to change who they are,' Theresa May said in an interview with PinkNews. 'We're looking carefully at the extent of the problem, and the experience of other countries that have introduced bans, to ensure we get the approach to this right.'

Evangelicals on synod, who believe the Bible teaches gay people should remain celibate, agreed that 'gay cure' was 'very damaging' because it suggested homosexuality is an illness.

A statement from Living Out, a group of conservative gay Christians, says: 'Attempting to change someone's sexual orientation assumes that being gay is somehow more problematic than being straight.'

Mike Davidson, a gay conversion therapist from the Core Issues Trust, told Christian Today: 'There is no motion or action from any professional body or denominational governing body that will extinguish the determination many individuals have to leave homosexual practices and desires, nor to dampen the ardour with which their supporters provide care to such persons.'

He added: 'The unholy alliance between gay activists and those within the Church of England who promote the idea of "born gay" is revealing in its lack of respect for personal freedom to choose pathways consistent with belief.'

Under a separate motion the Church will also consider special services to mark a transgender person's transition.

The move could see baptism-style renaming ceremony for people who wish to change gender.

Already in place in some Baptist churches and others, the Church's most senior trans priest, Rev Rachel Mann, Rector of St Nicholas Burnage and a minor canon at Manchester Cathedral, welcomed the suggestion for formal Anglican liturgy.

She previously told Christian Today: 'Trans people feel powerfully called to be recognised in their 'chosen' name. An opportunity to be publicly introduced to God is therefore significant. I think this is what the proposed liturgy aims to do.

'It will be symbolically powerful. The extent to which it is [a form of] baptism will be debated by General Synod of course, but this liturgy is a welcome move to affirm Trans people.'

The CofE's position on transgender people accepts that differing views can 'properly be held' on the subject but the motion is likely to receive opposition from conservative synod members.

Clive Scowen, a senior evangelical on synod, told Christian Today authorising liturgies was not a 'sensible thing to do' and said clergy should be able to devise individual responses for each person.

'People who have gender dysphoria must be treated with the utmost love and pastoral sensitivity, and of course warmly welcomed in our churches,' he told Christian Today. 'I am far from convinced that surgical or medical intervention to try to reassign gender is a loving response. I do not think that scripture supports the idea that gender, which is a physical fact about a person's identity (whether assessed by reference to chromosomes or genitalia), can be changed; rather I do believe that the Holy Spirit can bring change to how a person perceives gender to conform it to the physical facts.'

The main focus of the four-day sitting in July will be a presentation from bishops on the Church's next steps on teaching on sexuality after a report keeping the doctrine of marriage as between one man and one woman was rejected by the synod in February.

A heated question and answer session will follow as synod members try to probe the direction the CofE is taking and what Justin Welby means by the 'radical, Christian inclusion' he has called for.