The Welsh government faces pressure to abandon plans that would force church youth groups to be inspected and outlaw "unregistered churches".

A coalition of evangelical charities issued a joint statement on Monday that blasted the proposals as an "unjustified restriction of religious liberty". The plans would require any out-of-school educational setting that taught children above a certain threshold to register with the government. Many church youth groups could fall above the threshold and therefore have to join the register and face inspections by government officials.

The Welsh government has said churches will not inspected unless there is a complaint. However the charities warned the "scope for for vexatious complaints is considerable, especially in the current climate of aggressive secularism and religious illiteracy".

CARE, Christian Concern, the Evangelical Alliance, the Evangelical Movement of Wales, the Lawyers' Christian Fellowship and The Christian Institute said the Welsh government should not appoint "a state regulator of religion". They added: "For an inspector to scrutinise a Sunday School class, Bible study, youth meeting or church weekend away would be highly intrusive. The prospect of inspectors questioning volunteer leaders and children (without their parents) is an unwarranted incursion into private religion and family life."

The six charities issued a rallying cry to their supporters and called on them to urge assembly members to oppose the plans.

"Christians are peace-loving, law-abiding citizens who respect authority and love their neighbours. They are a major source of volunteering. To require such people to submit to registration and inspection to ensure they are not engaged in "undesirable teaching" is profoundly misconceived," the statement read.

Representatives of the six charities warned churches work with young people would be damaged by the plans. Simon McCrossan, the Evangelical Alliance's head of public policy, said the proposals "will do little to make children any safer from violent extremism and will jeopardise historic religious freedoms in Wales".

Mark Jones, chairman of the Lawyers' Christian Fellowship, said he had "grave concerns" about the plans. He warned they would be "counter-productive" and "may arguably place the UK in breach of its international human rights obligations".

Gareth Edwards, general manager for the Evangelical Movement of Wales, added: "We understand the need to combat extremism and safeguard children and are committed to being transparent about the Biblical teachings at the heart of our activities.

"However, we do not believe Government inspectors should police Christian youth work, and consider the subjective nature of some of the proposed criteria, such as 'tolerance', to be too vague and open to abuse".