Religious groups must comply with data protection laws, the European Court has warned, as it rules that Jehovah's Witnesses must ask permission before collecting personal data on the doorstep.

In a ruling made following an appeal by the Finnish arm of the religious group, the Court of Justice of the European Union said that they must gain consent from householders before collecting their data.

It comes after the Church of England told members not to distribute people's personal data in written prayer requests following the introduction of GDPR, the EU's new data privacy law, earlier this year.

The case was brought amid confusion over whether the Jehovah's Witnesses information gathering was exempt from privacy laws because the data was not filed centrally and was used by a religious group in the act of door-to-door preaching.

The judgment said that the group keeps a list of people who have asked not to be contacted, known as a "refusal register", as well as "the name and addresses of persons contacted, together with information concerning their religious beliefs and their family circumstances".

The information is "collected as a memory aid and in order to be retrieved for any subsequent visit without the knowledge or consent of the persons concerned".