Christian schools with pupils only from one ethnic or religious background may be forced to ensure children from other faiths are included, under the government's integration plans published today.
The 'integrated communities strategy' aims to tackle 'worrying levels' of racial segregation and social exclusion highlighted in a 2016 report by the government's former integration tsar, Dame Louise Casey.
Current guidance means schools must teach about cultures and belief systems other than their own, which, for example, means Church of England schools must teach about same-sex marriage. But the plans published today by the communities secretary Sajid Javid, backed by £50million of government funding, will take this further.
Mr Javid said: 'Britain can rightly claim to be one of the most successful diverse societies in the world.
'But we cannot ignore the fact that in too many parts of our country, communities are divided, preventing people from taking full advantage of the opportunities that living in modern Britain offers.
'Successive governments have refused to deal with the integration challenges we face head on, preferring to let people muddle along and live isolated and separated lives.'
Education secretary Damian Hinds added: 'We want to make sure that all children learn the values that underpin our society - including fairness, tolerance and respect.
'These are values that help knit our communities together, which is why education is at the heart of this strategy.
'It's also important that children are taught in a safe environment and that we can act quickly if children are at risk or being encouraged to undermine these values.'
The strategy also targets Islamic communities after Casey warned some Sharia councils are engaging in discriminatory practices against women and operated a parallel legal system that denied women and children access to their rights.
'There have been claims that some Sharia councils have been supporting the values of extremists, condoning wife-beating, ignoring marital rape and allowing forced marriage,' she said in her report.
Now Imams who marry Muslim couples without registering it under British law could face prosecution in the new government guidance.
It is thought around 100,000 Muslim women in Britain have been married in Sharia councils, meaning their marriage is not recognised under UK law and they do not have the same protections in divorce proceedings.
