Seventy Church of Engand and Roman Catholic bishops were urged today to intervene to help thousands of Christian students at British universities from having the organisations representing them banned.

Among those asked to take action to save Christian Union societies were the Archbishops of Canterbury and Westminster.

The rise of secularism in the UK is among the issues being debated today and tomorrow at the first ever joint meeting of the Anglican and Roman Catholic bishops of England and Wales in Leeds.

Dr Rowan Williams and Cardinal Cormac Murphy-O'Connor were to issue a joint statement later today on the importance of working together and how to surmount the differences that remain between the two churches.

The 40 Anglican and 30 Catholic bishops began their unprecedented two-day meeting at Hinsley Hall at lunchtime. The bishops prayed and worshipped together and discussed how to heal the historic rift between them.

But Christian Union leaders urged them to move away from the usual "bland platitudes" associated with ecumenical gatherings to help the beleaguered Christian student societies under threat of bans.

Dr Peter May, member of the Church of England General Synod and head of the Universities and Christian Colleges Fellowship, said in a letter sent individually to each bishop: "We would respectfully invite you and your colleagues to consider, for a few moments within your crowded agenda, the very difficult position thousands of Christian students are facing in higher education establishments right now.

"The negative and abusive use of equal opportunities policies and anti-discriminatory policies by student unions and student guilds are placing great strain on Christian unions."

Dr May continues: "If CUs uphold orthodox Christian teaching, they can find themselves banned from using campus buildings for their activities or promoting them, their SU [Students' Union] bank accounts frozen, and removed from the official list of SU societies on campus."

The three cases cited include Birmingham University Christian Union, banned from the official list of societies after it refused to amend its constitution to allow non-Christians to become executive committee members; Exeter University Christian Union, ordered to change its name to Evangelical Christian Union and suspended until it complies, and Edinburgh University, where the Christian Union has also been banned and was refused permission for a Bible-based course on relationships to be run on campus.

The Exeter Christian Union has served notice on the university and the Guild of Students that it is taking legal action against under the 1998 Human Rights Act. The European Convention on Human Rights protects "freedom of religion, expression and association."

Bishops from both the churches are leading the fight back against secularisation.

In an address last week the Archbishop of York, Dr John Sentamu, said: "In the fear of not offending someone, the illiberal atheists, under the cloak of secularism, end up offending everyone, acting out of the mistaken belief that religion should be a private matter and that faith itself should be privatised."

Tomorrow night Dr Rowan Williams will launch Britain's first research project into the nature of the relationship between religion and civil society.

The Manchester Research Institute for Religion and Civil Society will analyse how religion relates to public and private sector service provision, globalisation, political economy, democracy, belief, secularism and political action on climate change.

In a lecture to academics, students, members of faith-based organisations, politicians and policy-makers, Dr Williams will look at how ideas of political freedom and religious freedom come together in a developed society. The Archbishop said he will challenge "some popular definitions of a secular society and suggest some priorities for communities of faith in the present context."

Dr Williams will also make a major intervention on the subject of faith and secularism next week when he flies to Rome for an audience with Pope Benedict XVI.

The Archbishop's first official visit to Rome since he met the new Pope at his inauguration has been organised to commemorate the 40th anniversary of the visit of the late Archbishop Michael Ramsey.

The 1966 meeting is regarded as an ecumenical milestone because it led to the setting up of the Anglican-Roman Catholic International Commission (Arcic) and to an era of unprecedentedly warm relations between Catholics and Anglicans.

Relationships have cooled recently because of the ordination of women priests and bishops in some parts of the Anglican Communion, and more recently the consecration in 2003 of an openly gay bishop in The Episcopal Church in the US. Advisers spoke openly of an "ecumenical winter".

But against some expectations, Pope Benedict XVI has shown himself to be an enthusiastic promoter of dialogue. It is hoped that his meeting with Dr Williams will lead to the setting up of the third round of talks under the Arcic umbrella, in which greater sharing of buildings and non-eucharistic services could be promoted.

Both sides hope that this might forestall divisive argument over self-evident doctrinal differences and encourage a more "organic" move towards unity from the parish pews upwards.

Dr Williams will throughout his visit wear the symbolic episcopal ring that was given to Archbishop Ramsey by Pope Paul VI.

Archbishop Geoffrey Fisher was the first Archbishop of Canterbury to meet the Pope when he had an audience with John XXIII in December 1960.