All teachers who want to work in Catholic schools will have to seek personal approval from the Church under confidential plans drawn up by Scotland's largest local authority.

The move in Glasgow marks a significant escalation in the rights of the Catholic Church over the employment or promotion of teachers in Catholic schools on the grounds of their "religious belief and character". There has already been a furious backlash to the proposals from officials at the Educational Institute of Scotland (EIS), Scotland's largest teaching union, who believe it flouts employment regulations.

There have also been warnings from Glasgow City Council itself that the authority could face legal action from unsuccessful candidates unless the Scottish Executive changes the law.

The new recommendation, contained in a confidential paper seen by The Herald, could ultimately clear the way for the Church to vet all teachers in each of Scotland's 391 Catholic primaries and secondaries.

The paper, which will be considered by the council's executive committee in August, follows an employment tribunal last year involving a teacher called David McNab which restated the Church's right to approve all teachers in its schools.

Although the right was enshrined in the 1980 Education Act, it has never been fully observed, with many councils, including Glasgow, choosing instead to reserve only specific posts, such as that of headteacher, for Catholics.

Following the McNab ruling, the Scottish Catholic Education Service (SCES), set up by the Church to promote the distinctive nature of denominational education, said all teachers applying for a job should provide the name of a referee to testify to their commitment to Catholic schools.

In addition, teachers should agree to promote the values set out in the Charter for Catholic Schools in Scotland, which states that teachers should have a commitment to uphold the moral teaching, faith tradition and sacramental life of the Church.

After considering the tribunal's findings, council lawyers decided that abiding by the SCES guidelines provided the "best attempt" to reconcile tensions between the Church's right and employment regulations drawn up in 2003 which make it unlawful for an employer to discriminate against someone on the grounds of religion or belief.

However, officials also warned in the confidential document: "It may ultimately be that this tension can only be resolved by the Scottish Executive or a superior court."

Last night, officials from the Glasgow branch of the EIS said they intended to oppose the council plans. Willie Hart, branch secretary, said: "The EIS nationally has a policy of equality of opportunity in employment regardless of race, religious gender or sexual orientation, and this development would appear to diminish that.

However, Neil Roarty, chairman of SCES, welcomed Glasgow's move and said he hoped other local authorities would follow its example. He said: "This is not about denying people access to Catholic schools. It is about ensuring that all those who work in Catholic schools, of whatever faith, are prepared to uphold the distinctive aims and values of Catholic education."

Gordon Matheson, the council's executive member for education, said: "As a consequence of the outcome of the McNab case, the council has revised its approval policy for teachers applying for posts in Catholic schools."