Employers are allowed to bar workers from wearing headscarves provided restrictions on religious garments are applied to employees of all faiths, the European Union's top court ruled on Tuesday, in a decision that could shape the place of Islam in public life on the Continent.

In its ruling, the Luxembourg-based European Court of Justice said that internal regulations banning "the visible wearing of any political, philosophical or religious sign" did not constitute direct discrimination.

The court also said that, in the absence of a general ban on religious symbols, employers could not prevent a worker from wearing a headscarf simply because a customer demanded it.

The decision by the court comes as countries across Europe are grappling with how to accommodate huge numbers of migrants, many from predominantly Muslim countries in the Middle East and Asia. Nationalist, right-wing parties have seized on the issue of Muslim immigration to build support before elections in France, Germany and the Netherlands.

The decisions of the European Court of Justice, which interprets the law for the 28-nation European Union, are binding on member states. Legal experts said the headscarves ruling could have far-reaching consequences for the balance between freedom of religion and the rights of companies across the bloc to put in place policies requiring religious neutrality.

Rights advocates criticised Tuesday's decision, saying that it undermined the guarantee of equality.

Maryam H'madoun, a policy adviser with the rights organisation Open Society Foundations, said that in many EU member states, national law would still recognise that a ban on religious headscarves at work constituted discrimination.

She expressed concern, however, that the ruling would exclude many Muslim women from the workforce in countries where the laws on wearing religious symbols are different.

"This disappointing ruling weakens the guarantee of equality that is at the heart of the EU's anti-discrimination directive," H'madoun said.