A widespread campaign to rid Church schools of Christianity is under way, according to local clergy near where a school was forced to ban a Christian group from taking lessons or assemblies.

St John's Church of England Primary School in Tunbridge Wells agreed to block CrossTeach, a Christian charity, after complaints from a number of parents who said children were being told 'men can't marry men' and 'they would not go to a good place when they died' if they did not believe in God.

But the orchestrated campaign goes further and demands the removal of crosses, Bibles and even the banning of Church of England clergy from Church of England school assemblies, according to local clergy in Tunbridge Wells.

A 13-page briefing document circulated by concerned parents to raise support and seen by Christian Today includes criticism of a 'large cross' at a worship area in the school and specifically demands Jono Chalklin, the youth leader at local St John's Church, not take any more assemblies.

The pamphlet, written by the St John's Concerned Parents group, cites Twitter posts by Chalklin unrelated to his work at the school as 'evidence' of his unsuitability. Among them is a retweet of a post quoting lines from William Cowper's hymn, 'There is a fountain filled with blood'. It demands the headteacher remove any links to groups with 'an evangelistic agenda'.

Rev Peter Sanlon from the nearby St Mark's Church and Rev Giles Walter of the school's affiliated St John's Church, who has been taking assemblies there for 24 years, accused parents of launching a 'hand-grenade' into a happy environment and said it was they who were 'extremist', not the Christian teaching in the school.

Sanlon told Christian Today the parents' 'bullying tactics' would never have been tolerated against a minority group other than Christians and 'have intimidated and victimised other parents and school staff'.

He went on to attack the Diocese of Rochester for failing to stand up for the school after the director of education thanked parents for raising concerns around CrossTeach but offered no defence.

'We are witnessing the impotence of England's great institutions,' he told Christian Today.

'This is no playground squabble, it is the car crash of England's great institutions as they are revealed to be unable to uphold their own convictions or heritage.

'The pressure group are complaining about clergy and the Diocese of Rochester Collective Worship programme - but the Church of England has thus far struggled to defend itself publicly. The pressure group are using the governments's PREVENT Strategy and undefined "British Values" to portray mainstream Christianity as extremist. This is precisely what the government was warned would happen.

'This dispute in Tunbridge Wells is highlighting the inability of both our government and the Church of England to effectively preserve freedom of religion and diversity. As the bullies are allowed to have their way, all suffer.'

It comes after John Constanti, the interim director of Rochester Diocesan Board of Education, said: 'The Government is clear that schools should ensure that the content of any assembly or act of collective worship should be appropriate for the pupils who are taking part, and that it should allow for pupils who are not part of Christian families to join in. The Diocese of Rochester is committed to this principle and works closely with schools to ensure that religious education and collective worship are engaging, respectful and useful to students in helping them to live in a diverse society – we will continue to do this across all of our schools.

He added: 'We are grateful to parents for raising this issue with the school. Church of England primary schools seek to offer a broad education to children and young people, while always being respectful of the diversity of pupils' cultures and beliefs.'

Walter, who leads the primary school's linked church, also hit back at the parents saying he had never been asked to 'withdraw, or apologise for, anything' he had said or done at the school until now.

'The behaviour of this small group of parents has hurled a hand grenade into a previously happy and harmonious environment. They seem determined to drive mainstream Christian teaching out of our church school: and it is they and not ourselves who should be charged with extremism and non-inclusiveness,' he said in a statement to Kent Live.

The national director of CrossTeach, Wayne Harris, agreed the issue was wider than just the charity's teaching and said the parents' complaints relate to comments made by other people not involved with CrossTeach.

He told Christian Today the campaign was part of a wider campaign against Christianity rather than just his charity.

'Some of the things that have been mentioned have all been attributed to us but they do not all come from activities we have done,' he said.

'They have bunched them all together.'

Christian Today has contacted the St John's Concerned Parents group for comment.