Justin Welby today became the first Archbishop of Canterbury to address those gathered for the annual National Parliamentary Prayer Breakfast in Westminster, in an eloquent speech which highlighted the key tenants of the modern Church.

The breakfast provides an opportunity for MPs, peers, church leaders and charity representatives to come together and celebrate the work being done by Christians across the UK, while also discussing the challenges that the Church faces in modern society.

Organised in partnership with Christians in Parliament and the Bible Society, the prestigious event was even this year attended by David Cameron and Ed Miliband, the first time ever that a Prime Minister and Leader of the Opposition have both made an appearance.

Following readings from Isaiah 58: 6-12 and Acts 2:43-47, the Archbishop opened his address by thanking those present, and declaring that the Church should always be more than just "useful".

"I hope and pray that we will never just be useful – what a dreadful condemnation that would be," Welby said, before joking that "the walls of Lambeth Palace are lined with Archbishops looking useful, a bit like Hogwarts".

"There have been moments when we've fallen into that trap," he continued. "But it's always happened when we've lost sight of the fact that at the heart of being a Christian is knowing Jesus Christ, so that together as we meet with him and share in worship, we find ourselves renewed and strengthened for the call of carrying the cross and following him."

Welby pointed to the suffering of the Church, particularly in countries where Christians face horrendous persecution, but noted that it is in times of suffering that the Church finds courage, experiences real growth, and is able to offer hope to the global community.

"The global Church is a profoundly suffering Church. It is cross-shaped. It carries a cross of suffering, but also it carries a cross for the salvation of the world," he shared.

"That has always been a scandal since the first few centuries. Early doubters, attackers of the Christian Church, said: 'How can you worship someone who died on a cross?' But it is a scandal of which we should be proud. We boast in the cross of Christ. It tells us that each of us here – each of us, all of us – need God's rescue because we cannot rescue ourselves.

"It calls us, the cross, to prayer and worship, passionate devotion to Jesus, who died for us. The Church of the 21st century clings to Christ in prayer, finds its strength in prayer and prays together."

The importance of unity was intricately woven throughout Welby's speech, as he underlined the vitality of offering one another "radical" grace, particularly as the Church grapples with divisive issues such a women bishops and same-sex marriage.

"We [the Church] belong to one another not because we choose to but because God has made us that way; you can choose your friends, but you're stuck with your relatives, and I have to tell you that all who follow Christ are relatives, so you're stuck with me and I'm stuck with you, so we'd better get used to it," the Archbishop joked, adding that this understanding is "essential" to the practical outworking of the Christian faith.

"We do not have the option, if we love one another, of simply ditching those with whom we disagree," he said.

"You don't chuck out family; you love them and seek their wellbeing, even when you argue. In the Church of England we are seeking to start a radical new way of being the Church: good and loving disagreement, a potential gift to a world of bitter and divisive conflict.

"What can be more radical than to disagree well, not by abandoning principle and truth, but affirming it – agreeing what is right, acting on it and yet continuing to love those who have a different view?

"The struggle, the achievement, of holding together in good disagreement sets a pattern in which truth is not a club with which to strike others, but a light freely offered for a path of joy and flourishing," he declared.

Just yesterday Welby met with Pope Francis in Rome, the second time the pair – who are said to enjoy a close friendship – have met in eighteen months. Perhaps inspired by their meeting, the Archbishop drew on Francis' passion for the poor and vulnerable in his address this morning, noting that, "The poor are not served by a divided Church obsessed with inward issues...When we listen to God we are looking outwards, not inwards.

"God has no preferences, except a preference of love for the poor, the week and the vulnerable; the widow and the orphan, the alien and the stranger," he continued.

"The Church is the most effective Church when it demonstrates that love...Love and outward-looking should be the characteristic of the Church. Holiness, radical difference in lifestyle. And truth and love drive action and attitude."

Welby concluded his address by insisting that the modern Church must be a prophetic voice in standing for "human dignity".

"A 21^st-century global church loves the poor and the victim...challenges oppressors and supports victims. It speaks for women killed in lynchings called "honour killings", or for those imprisoned under blasphemy laws. It does all that despite its own suffering. Truth and love embrace," he said.

"The church is not an NGO with lots of old buildings. It is the Church of God, rejoicing in the realities of cultural diversity in a way never known before: global, cross-bearing, confident and welcoming," the Archbishop finished.

"The global Church is above all God's church, for all its failings, and in passionate devotion to him will offer the treasure He puts in our hands, unconditionally, always pointing in worship, deed and word to Jesus Christ. Amen."