Germany's federal labour court on Tuesday upheld the right of religious institutions' employees to go on strike but said it only applied under certain conditions.

The court case arose after charitable and parish organisations in western North Rhine-Westphalia state complained about strike action launched in 2009 by, among others, the Verdi service-sector trade union.

Employees of Churches and other religious institutions such as charities are governed by their own labour laws in Germany, providing a wide degree of autonomy in terms of pay and working conditions.

Unions wanted to compel religious bodies to adopt regular labour agreements.

In a ruling welcomed by both Verdi and the German Bishops' Conference -- each of which interpreted it as a victory -- the federal court in the eastern city of Erfurt said labour laws governing the Churches and religious bodies remained valid.

And it confirmed religious employers' right to opt for a joint commission of Church and staff representatives to agree on working conditions which cannot be contestedlater.

Trade unions must be represented on these commissions, the court insisted, and added that if this was not the case, the right to strike would apply.

The ruling affects nearly 1.3 million people.