Pope Francis wants to make it easier for Catholics to have their marriages annulled.

But his reforms to achieve that are regarded with suspicion by conservatives wary of the de facto introduction of Church-approved divorce.

Details of significant reforms of a system that critics, including Francis himself, have attacked as needlessly bureaucratic, expensive and unfair were due to be unveiled on Tuesday with the publication of letters on the issue from the Pope to Catholic churches across the world.

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Vatican experts in canon, or religious, law have spent the last year studying how the system could be streamlined without undermining the principle that marriage is for life.

That is one of the fundamental tenets of the Catholic faith, albeit one at odds with the reality that, across much of the industrialised world, divorce is commonplace even among believers.

Church doctrine does make allowance for unions to be effectively cancelled, subject to certain conditions.

Essentially, a church tribunal must rule that the marriage was fundamentally flawed from the outset and that ruling must then be upheld by a second tribunal.

Possible justifications for reaching this conclusion include the marriage having never been consummated, one or both partners having entered into it without the intention of staying in the relationship, or one of the partners having no desire to have children.

Alcohol and drug dependency can also be taken into consideration when a tribunal decides whether a marriage can be annulled.

In practice, the process of securing an annulment is frequently extremely lengthy.

In many parts of the developing world, dioceses simply do not have annulment tribunals.

And where they do exist, many ordinary Catholics cannot afford to employ the expert help needed to guide them through the arcane procedures required to secure the necessary approval.

Francis has repeatedly expressed the wish that the system should be free and made equally accessible for rich and poor believers.

Ideas under discussion include abolishing the need for a second church court to review and uphold an annulment.

The experts have also discussed making it easier for Catholics married to non-believers to obtain annulments on the grounds of their partner’s lack of faith.