Cardiff, UK - The UK Border Agency (UKBA) says it is working with Church in Wales to train clergy to spot fake marriages.
It comes after immigration officers stopped a fake marriage ceremony in a church in the Canton area of Cardiff last week.
The Church in Wales said it has seen a "significant increase" in potentially bogus applications over recent years.
"We are setting up awareness-raising sessions to help clergy spot sham weddings," said the UKBA.
Abigail Corbett, who heads the UK Border Agency's Local Immigration Team for Cardiff and south east Wales, said clergy would be given tips on how to spot fake identity documents and help on establishing whether a relationship was genuine.
"We are already carrying out a great deal of work with the Church in Wales to crack down on sham marriages and more is planned."
Ms Corbett said both the UKBA and the Church in Wales was taking the issue of sham marriage very seriously.
"We recognise that we have to work together to stop it and tackle the criminal gangs behind it," she said.
"Our local immigration team works with many other organisations - including the church - to crack down on abuses of the immigration system.
"Our door is open to anyone who needs help or advice, or has information on abuses of the immigration system."
A spokeswoman for the Church in Wales said: "Applications for marriage from foreign nationals are not that common in our churches.
"However, some parishes have seen a significant increase over the past few years - about one a month - and we are concerned that many of them may be fake."
The spokeswoman added that while the church was sympathetic to people prepared to take desperate measures to live in the UK, it believed they should act within the law and not abuse the sacred sacrament of marriage.
Deportation
"We advise our clergy to be aware of the issue, and to insist on seeing valid identification such as passport or visa which shows a name and photograph and to interview both parties," said the spokeswoman.
"They should report any suspicions they have to the diocesan registrar or the Border Agency for further investigation."
Sham marriages usually involve a non-European marrying someone from the European Economic Area in a bid to secure long-term residency, the right to work and the right to claim benefits in the UK.
Two Nigerian nationals, a 52-year-old woman and a 51-year-old man, arrested at St John's church, Canton, Cardiff, on Friday have been transferred from Cardiff to an immigration removal centre pending their deportation over the coming weeks, said the UKBA.
The woman, who planned to marry a Portuguese national, had provided false identity documents to the church authorities ahead of the wedding.
She has since been confirmed as a failed asylum seeker who had remained in the UK illegally when her claim for protection was turned down.
The Nigerian man had previously also been confirmed as a failed asylum seeker.
The Portuguese groom, 50, received a warning.