Turkey should have a religious constitution, parliament speaker Ismail Kahraman said on Monday, in comments that will likely add to concerns of creeping Islamisation under the ruling AKP party.

"As a Muslim country, why should we be in a situation where we are in retreat from religion?" state-run news agency Anatolia quoted him as saying.

"We are a Muslim country. As a consequence, we must have a religious constitution," the AKP lawmaker told a conference in Istanbul.

"Secularism cannot feature in the new constitution."

Critics accuse president Recep Tayyip Erdogan's Islamic-rooted AKP of eroding the secular values laid by modern Turkey's founder Mustafa Kemal Ataturk since it took power in 2002.

Over the past two years, the government has lifted bans on women and girls wearing headscarves in schools and civil service.

It also limited alcohol sales and made efforts to ban mixed-sex dorms at state universities.

Kemal Kilicdaroglu, the head of Turkey's main CHP opposition party, slammed the speaker's comments.

"The chaos that reigns in the Middle East is the product of ways of thinking that, like you, make religion an instrument of politics," Mr Kilicdaroglu wrote on Twitter.