The inquiry, which will report by June, will be conducted by a committee dominated by conservative MPs, including the Liberals David Clarke and Marie Ficarra, and Mr Nile's colleague Paul Green.

It will examine the objectives and effectiveness of the classes, the curriculum and whether the legislation that allows them to be taught as an alternative to special religious education should be repealed.

The government will also establish an annual ''celebration of special religious education'' to recognise the efforts of scripture teachers.

It will mandate that scripture be made available for a minimum of 30 minutes a week of ''meaningful teaching time'' in primary schools and a minimum of one period a week in secondary schools.

The 30 minutes minimum will also apply to ethics classes. Current policy sets only maximum times for both. In another change, providers of special religious education will be told how many parents tick the ''religion'' box when enrolling their child, so they can plan classes better.

The government moved for the inquiry to be established yesterday during debate of Mr Nile's private member's bill that seeks to abolish ethics classes. The Herald revealed in July that Mr O'Farrell met Mr Nile to discuss that bill after Mr Nile said he would consider using his party's numbers in the upper house to block passage of the government's industrial relations laws.

At the time Mr O'Farrell denied a deal had been struck over ethics classes, which he and the Education Minister, Adrian Piccoli, had promised to retain during the election campaign.

Mr O'Farrell acknowledged he told Mr Nile during the meeting that his bill would be considered by the Coalition party room and cabinet, but said that was a courtesy afforded every MP who introduced a bill.

Two months ago Mr Piccoli told Parliament there were ''currently no plans for a review of ethics classes in 2012''.

Mr Nile confirmed he discussed ethics classes at a meeting with Mr O'Farrell two weeks ago and that the Premier said he would ask Mr Piccoli to meet him, which he did.

''This will be the first time there has been a formal investigation into the ethics classes,'' Mr Nile said.

Mr Piccoli said the minimum class times and annual celebration were designed to ''strengthen'' the teaching of special religious education.

The opposition education spokeswoman, Carmel Tebbutt, said the government had chosen to ''abandon the promise they made before the election, place the classes under a cloud and use ethics classes as a political football. That's not fair to children." She accused Mr O'Farrell of doing a deal with the crossbench.

But Mr Piccoli said ethics classes ''will remain in government schools because the government believes that there ought to be an alternative provided for students who are not taking scripture classes''.

The executive director of the St James Ethics Centre, Simon Longstaff, said the inquiry was ''unhelpful'' as it created uncertainty for parents, students and volunteer ethics teachers.

But Dr Longstaff, whose centre devised the classes, supported the right of the Parliament to scrutinise the classes. ''The matter seems to have been settled on so many occasions, only to be revisited in a way that if it was any other matter would be just unfair,'' he said.

The Greens MP John Kaye said Mr Nile had ''extracted a bizarre price for his on-going support of the O'Farrell government in the upper house.''