The six organisations claim that the legislation discriminates and want it to be abolished.
As a result of the new law Belgians and non-EU citizens have to show that they can meet the extra maintenance costs if they get a relative to join them in the country.
The six organisations include ADDe, Ciré, Ligue des Droits de l'Homme, MRAX and Siréas. They argue that the new legislation violates the fundamental right to a family life. They say that the law introduces discrimination on the basis of wealth. They feel that the authorities should consider individual cases instead of insisting that a minimum amount of money has to be available to ensure that new relatives can be maintained.
They also argue that Belgium's new law is not in line with rulings of the European Court of Justice. They say that it's particularly Belgians of Turkish and Moroccan extraction who will be most badly hit by the legislation and that this suggests it is discriminatory.
The six also condemn a lack of transition measures. People who filed an application under the old system are now being confronted with new rules.