Labour leader Keir Starmer has called Christians the "moral compass" of his party and praised their "leadership" during the pandemic.

Starmer was the special guest at a church service on Sunday organised by Christians on the Left to coincide with the Labour Party's annual conference in Brighton.

"You're the moral compass of our party and that has helped me and guided me and guided our party and I'm truly grateful for everything you have done for all of us," Starmer said.

He added later, "All politics needs that moral compass, that sense of the 'bigger' than the political decisions and the policies, and you provide that for us and I'm deeply grateful for it."

Elsewhere in his address, Starmer thanked Christians for their "leadership" during the pandemic, whether by running community projects like foodbanks or simply knocking on doors to check on people.

"That coming together and recognising our common humanity, that in a time of crisis we needed to look after each other ... for me it's probably one of the most important political moments since Thatcher said 'there's no such thing as society'," he said.

"It really is, because what it showed to me is that when push comes to shove, when there is a crisis actually as humans, humanity trumps, we pull together in an incredible way and a lot of that was done through churches, a lot of that was done through faith, whether that's foodbanks, support, going out to our communities and even just knocking on the door and talking to people ... and it was very, very powerful."

He added, "Thank you for everything you did to sponsor and support that ... but also thanks for the leadership because actually you and others led the country into this frame of mind that has been so powerful in this pandemic."

The church service also heard from Jonathan Reynolds MP, Shadow Secretary of State for Work and Pensions, and Chair of Christians on the Left.

"There are Christians involved in some of the most important and vital work that's going on up and down this country and no one for me will ever put it better than the great Desmond Tutu who said there comes a point where you need to stop just pulling people out the river, you have to go upstream and find out where they're falling in.

"My friends, there are far too many people in this country and around the world who are in that river right now. So as Christians, frankly, we have to be involved in politics," he said.

Stephen Timms MP led prayers during the service for an end to injustice, war, and vaccine inequality, and for refugees coming from Afghanistan.

"May people around the world be prepared to open their hearts to welcome them," he said.

The sermon was delivered by Natalie Williams, CEO of Jubilee Plus, who said mercy had become rare in public life.

"But it shouldn't be rare. It shouldn't be rare among us as Christians but it shouldn't be rare in our society because we are called to be mercy bringers," she said.

"That's what it means to love our neighbours, whether it's prayerfully, politically, practically. In any which way, it means to bring the mercy of God into our communities, into our streets, into our workplaces, into conferences, into church services."

She continued, "It's rare in public life, it's rare on social media, it's rare in political debate. We only need to look at debates around subjects like universal credit or immigration and security of our borders, the pandemic, the Brexit debate.

"I don't think any of those have been saturated with mercy."