Delivering the opening address at the Mission21 conference in Bath on Tuesday, Martyn Atkins said the need for variety was essentially missional but also political in light of a society that is becoming increasingly distrustful of religious groups whilst at the same time recognising the "bonding and bridging capital" that renders them necessary.
"We find ourselves in a political context where Christian communities are both regarded as dangerous and as vitally necessary. Consequently the mission opportunities are enormous and we must not miss the opportunities that the next two to three years will give us through another round of social and political change," he said.
Mr Atkins told church planters that the "fundamental" purpose of the church was to nurture disciples who would change the world through their discipleship and Kingdom values.
"For all its obvious nature and its rooted Christian command, disciple-making is not evident or even valued in many models of church. But one of the truisms of every renewal movement I can think of in history is that they were renewal movements partly or wholly because they were able to make disciples of Jesus Christ of people groups and populations that up to that point had largely been untouched by the Christian Gospel.
"In other words, Christian groupings that make disciples become renewal movements."
Mr Atkins warned that if fresh expressions of church and church plants were not making disciples "then what we are really doing is recycling existing susceptible believers".
He said churches needed to offer a sufficient "spiritual calorie intake" if people who became Christians were to remain and grow as Christians, and admitted that making disciples required a long-term commitment.
"The processes in such disciple-making much more resemble the long, hard, believing, belonging behaving, transformation associated with long term catechesis and formation rather than the shallow flimsy version of a tract at the end of a meeting or six quick lessons with the vicar before you enter confirmation," he said.
Hundreds of church planters and evangelists have gathered in Bath for the three-day Mission21 Conference, sponsored by Wycliffe Bible Translators, the Council for World Mission Europe, Together in Mission and the Group for Evangelisation.
Conference host Katei Kirby said the three days were an opportunity for church planters to discover, discern and discuss what God is doing to grow the church in the UK.
Conference delegates come from a variety of traditions and countries, including Germany, Switzerland, the Netherlands and Burma.