The annual Week of Prayer for Christian Unity got underway on Wednesday under the theme “We will all be changed by the victory of our Lord Jesus Christ”.

Parishes and congregations from different confessions and traditions around the world will hold special services and ecumenical celebrations throughout the week.

This year’s theme comes from St Paul’s first letter to the Corinthians, which promises the transformation of human life through the victory of Christ’s resurrection.

It was chosen by participating churches in Poland, who reflected on how their own faith sustained them through the many upheavals in their history.

The Week of Prayer for Christian Unity is traditionally celebrated from 18 to 15 January in the northern hemisphere, and around the time of Pentecost in the southern hemisphere.

Preparations are overseen by the World Council of Churches and the Roman Catholic Church.

Pope Benedict XVI said he hoped Christians would use the week to “ask God for the gift of full unity among the disciples of Christ”.

The Rev Bob Fyffe, General Secretary of Churches Together in Britain and Ireland, said: "When we pray for the unity of the church we are praying that the churches that we know and which are so familiar to us will change as they conform more closely to Christ.

"This is an exciting vision, but also a challenging one."