Turkey's education minister is to be the subject of a parliamentary inquiry over allegations of discrimination against religious students at the country's universities.
A motion centres on a ban on religious dress - in particular a ban on headscarves - enforced by the minister, Metin Bostancioglu.
Parliament voted last week by 230 votes to 209 to launch the investigation. After the vote the leader of the pro-Islamist opposition Justice and Development Party (AKP), Recip Tayyip Erdogan, called on the minister to resign.
AKP Istanbul deputy Irfan Gunduz promised protests if Mr Bostancioglu did not resign. But Mr Bostancioglu dismissed the calls, arguing that he had acted within the constitution and the law, and claiming that the controversy was about the future of the secular state.
The headscarf ban is part of Turkey's strict dress code, which forbids religious dress in public buildings. Although it had lapsed, a rise in support for Islamic parties saw the code's reintroduction in universities.
Supporters of the ban argued that it protected the country's secular education system, but it has resulted in thousands of women students being barred from education.
Mr Bostancioglu is a member of prime minister Bulent Ecevit's Democratic Left Party. Mr Ecevit is standing firm behind his minister. Speaking to deputies from his own party, he said the minister had his complete confidence and that there was no question of him resigning.
But it is widely believed that many members of the government voted against him. The ban is predicted to continue to be a source of division within the government.
Deepening divisions within the coalition have led to increasing speculation that the country will be forced into early elections within the year, with the ban expected to be a key issue.
The three-way coalition government is itself split over the headscarf ban. Leaders of the Motherland and National Action parties have voiced support for calls to end it. But the Democratic Left Party, which is the senior partner in the government, advocates its continued enforcement. All the opposition conservative and religious parties have called for an end to the ban.
Under a decree by the higher education authority, Yok, students who pass entrance exams could be disqualified if it were proved that they had worn a headscarf at the time. Each year thousands of women wearing Islamic headscarves and men with beards are barred from enrolling.
The ban has also spread to universities in the Turkish Republic of Cyprus.