Image via WikipediaOne of the realities many ecumenists encounter, locally through to international, is the separation of Pentecostal and Evangelical churches from the mainstream ecumenical movement. This has been addressed internationally through the Global Christian Forum in recent years.
I've found a blog post, A Funny Thing Happened on the Way to the Global Christian Forum, which summarises the origins of this split and the story of how the Global Christian Forum was founded.
Here's a an excerpt from the account of how the split was formed:
One concern Evangelicals and Pentecostals have often had is the loss of the missionary spirit among ecumenically-minded Christians—a terrible irony, considering that ecumenism was born at the Edinburgh Missionary Conference in 1910. The International Missionary Council that was formed as a result of the Edinburgh conference eventually joined the World Council of Churches in 1961; many Evangelicals left in protest. 1974 saw the formation of the Lausanne Committee for World Evangelization, following a Congress in the same place and year, at the initiative of the American evangelist Billy Graham. There 2500 Evangelical leaders from 150 countries recommitted themselves to world evangelization in signing the Lausanne Covenant. Clearly enough, they weren’t impressed by the WCC’s ability to keep up the missionary task of the church.
The post goes on to describe how the Global Christian Forum was founded and designed to compensate 'for their “underrepresentation” elsewhere, as well as to demonstrate the willingness of “ecumenical veterans” to be in the minority'.