The Archbishop of York has called on Christians to be peacemakers and not simply peace lovers, as he spoke of the power of the gospel to bring peace to difficult places at the 40th anniversary of the Christian International Peace Service (CHIPS).

Dr John Sentamu was guest speaker at the celebration in London last night together with former President of Nigeria, General Dr Yakubu Gowon.

In his speech, the Archbishop appealed to Christians to play their part in being active peace makers rather than simply passive peace lovers and build communities based on the love of Christ.

He said that a "great challenge" remained for those pursuing peace but assured that the "gospel has the power to do it".

"Christians must struggle to find ways to create communities which transcend tribalism, where we strive to love one another as God has loved us in Jesus," said Dr Sentamu.

He added, "The time has come, it seems to me, that this man of Nazareth, Jesus Christ, deeply lived out in small communities, we can actually become the channel in which instead of caste, deception, death the world finds the way, the truth and the life."

In his CHIPS anniversary speech, the Archbishop of York also warned of "militarism out of control" last night at the Christian International Peace Service, calling for the UN to be given a central role in mediating global conflicts.

"A scant regard for international law carries a high price, not only in terms of political uncertainty but more importantly in the body count which daily increases in those places where unilateral military action has proved so costly.

"In the short term such actions lead to quick victories, which make for great headlines. But the hard work of reconciliation, the hard labour of peacemaking ... never made it to the drawing board of those planning the invasion.

"We only have to look at the mounting daily death toll in Iraq to see the effects of military action without a concerted UN backing, where the consequences of militarist solutions play out against escalating sectarian and anti-western unrest ..."

The CHIPS anniversary also saw the organisation's founder and director for the last 40 years, Roy Calvocoressi, pass the leadership baton onto his successor Mark Cuthbert.

Cuthbert laid out his vision for the coming years when he announced CHIPS' plans to expand its operations to even more countries, including a new reconciliation project in West Africa and possibly in the UK.

"I invite us all to reflect on what part we can play in making this dream become a reality," he said at the celebration, hosted by longstanding CHIPS supporter Lord Donald Anderson of Swansea.

Earlier in the year, the Archbishop of York camped in a tent at York Minster where he fasted for one week for international peace in response to the televised pictures of the war in Lebanon. He shared his hope last night that the effort would encourage people to feel that there is something they can do to help.

Meanwhile, Dr Sentamu has dismissed as "tosh" suggestions that he is an Archbishop of Canterbury in waiting. He told an interviewer at BBC Radio York: "Rowan is a very close friend of mine. The Archbishop of Canterbury is unbreakable and from where I stand I can't have a better colleague than him ... The media are trying to do another Blair and Brown story but my response ... is: 'Sorry mate, it ain't like that; it just won't work.'"