Church leaders who came together last year to oppose a ban on conversion therapy have launched a new initiative affirming Christian teaching on marriage, sex and identity. 

The Greater Love Ministers' Declaration was launched in London on Tuesday and commits ministers to demonstrating pastoral sensitivity while rejecting the belief "that all sexual desires and inclinations are sacred" and upholding marriage as a union between one man and one woman for life.

The declaration invites ministers and pastoral workers from different Christian denominations to sign an affirmation of their shared beliefs on these issues and "the essential and unchangeable place of this teaching in Christian theology, its foundation in Christ's own example of self-giving love, and our duty and commitment as ministers of the gospel to uphold, teach and proclaim it".

It has been signed by over 800 church ministers so far. 

Rev Dave Gobbett, co-author of the declaration, lead pastor of Highfields Church Cardiff and Word Alive trustee commented: "In a day and an age in which people are so confused about what it really means to love one-another, and how to define love, in fact, it's more important than ever for Christian ministers and pastors to stand with the definition given to us by the Lord Jesus Christ in John 15:13.

"Christian ministry is always been about teaching and holding fast to the love that's defined by Jesus in his word."

Signatories of the declaration pledge to abide by Christian doctrine on marriage, sexuality and identity even if it means the threat of legal sanctions, financial penalties and social stigma.

"We will not surrender the 'Greater Love' that Jesus showed us, and to which he calls us, to the far lesser version of love which centres on the satisfaction and even the worship of self, the autonomy of the individual, and the belief that all sexual desires and inclinations are sacred," the declaration states.

"We will not accept that any perceived identities established by these beliefs justify departure from Christian teaching on marriage and sex. This is not, by our Lord's standards, love at all, and is profoundly harmful to many – children in particular."

Rev Dr Matthew Roberts, co-author of the declaration and minister of Trinity Church York, said it was important that church leaders make a public stand.

"Christianity has always held that marriage is only possible between a man and a woman, and that every person is made either male or female in God's image," he said.

"This is not only embedded in the gospel of Christ – who came from heaven to seek his bride, the Church – but it is a powerful force for good in lives and societies where marriage is honoured.

"These are vital truths which church leaders must stand up for publicly if we are truly to love God and neighbour as Jesus commanded us."

The co-authors of the declaration were also behind a letter to the government last year expressing concerns that a ban on conversion therapy would lead to the criminalisation of biblical teaching and prayer for people with unwanted same-sex attraction or gender dysphoria. The letter was signed by thousands. 

Dr Roberts continued, "The Greater Love Declaration has been signed by ministers and pastoral workers from all over the United Kingdom and what it affirms is that the love that we as Christians practice and teach, is modelled on Christ's love – that is a sacrificial love; life given up for the sake of others.

"There's an awful lot of talk about love today. But really what that means is something more like self-satisfaction or self-fulfilment. But Jesus explained in John 15:13 'greater love has no one than this, that someone lay down his life for his friends.'

"Now Christian teaching on marriage, on family, and on all human relationships, is founded on self-denial or self-sacrifice. So if you're a Christian minister or pastoral worker we would love you to read and sign the Greater Love Declaration, so that we can commit ourselves together to showing 'greater love'."

Dr Julie Maxwell, a community paediatrician and Church of England General Synod member, said children and vulnerable people were being put at risk by the prevailing ideology.

"Children and young people are growing up in a highly individualistic society where absolute truth is no longer taught, and judgements on morality are discouraged – consent seems to be the only limit," she said. 

"It has therefore never been more crucial that we teach them clearly about who we are, and how we are designed to live with respect to relationships and sexuality.

"To not teach these truths is to leave children and young people vulnerable to those physical and emotional harms which result from the experimentation with sexuality and gender identity that is encouraged by our society."

Rev Graham Nicholls, director of Affinity, said it was important that Christians "stand up for what the Bible teaches about sex and gender and the goodness of marriage".

"It's important that we teach it to our children. It's important that we speak to our culture about God's good design – about how it's best," he said.

"Sometimes that might go against the prevailing winds of culture, or go against what friends or family think. But it's the right thing to do."