Christians must not be silent as the "victory" of the sexual revolution spreads across the world, but neither should they condemn others, the Fourth Lausanne Congress on World Evangelization has heard.

Rev Canon Vaughan Roberts, rector of St Ebbe's, Oxford, told thousands of Christians gathered in Incheon, South Korea, that the sexual revolution had led to "the almost complete collapse of family life in our culture", with "devastating effects" on families and children.

"And ironically it hasn't even delivered the self-fulfilment that it was most designed to promote," he said.

"Look at the younger generation: isolated, confused - the anxious generation. The time when I was having to decide what subjects I would study onwards, we're asking them to decide: what is your sex, what is your sexuality?"

He said that the answer to the challenges lay in offering the world the love of Christ in a spirit of humility and compassion, as opposed to "Christian morality" and "a wagging finger". 

Speaking of his own experience with same-sex attraction, Roberts recalled being transformed by the love of Christ.

"Conservatives tend to be strong on repentance and holiness but too often we focus on moral rules rather than the wonderful relationship which Christ came to offer to us," he said. 

"It wasn't that I was suddenly gripped and excited by Christian morality. I was gripped and excited by Christ. I loved Him - and loving Him, I wanted to live for Him. So we need to offer to the world, not first and foremost Christian morality, but the Bible story - it's a love story."

He added, "Brothers and sisters, don't just preach morality. Certainly don't just preach condemnation. Preach and live Christ for the glory of His name."

Later in his address, he asked Christians to be mindful of their manner of engagement with people living by different beliefs and practices. 

"Such people are not just in the West, they're not just in the world. They're in this congress. They're in your country. They're in your churches. And too many feel unable to be open and honest about the struggles they feel for fear they'll be dismissed and rejected."

He continued, "Brothers and sisters, when we speak about these issues in church, will you always remember that people you're talking about are in the room. Does the tone and manner in which you speak invite them to be honest and open? Or does it force them into a secret, lonely isolation which will only be an incubator for the shame and sin?"

With the impact of the sexual revolution being felt far and wide, Roberts suggested there was no part of the world where Christians could be complacent. Rather, he said there was an "urgent" need for all churches to be ready to respond.

"We churches desperately need not to be silent - we've got good news to share," he said.

Christians in the Majority World were urged to pray for believers in the Western world as they seek to respond biblically, while Christians in the Western world were asked to pray for Majority World believers, that they would remain faithful.

Roberts cautioned churches not to give in to the temptation to compromise, warning that revisionist churches were "in terminal decline" and that such "adaptation" was not only "missionally ineffective" but lacking in "theological integrity".

Rev Roberts was speaking on the first full day of Lausanne 4, which is taking place in Incheon, near the South Korean capital of Seoul.

The weeklong congress has brought together over 5,000 Christians to strategise about how to fulfil the Great Commission and bring the Gospel to the whole world.

It is the first global congress to be held by Lausanne since Cape Town 2010.