Specialist officers from the UK Border Agency (UKBA) were based at Leeds Town Hall, speaking to every couple which included an EU national and a partner from a country outside the EU.
Of the 78 couples booked in to be interviewed by registrars during the operation, more than one in three chose not to get married on learning border officials were watching.
Ten pairings failed to turn up for interviews as word of the operation spread. Another 20 shelved their plans after being questioned by a UKBA immigration crime team.
Four suspects were arrested and face being deported after they were found to have been in the country illegally. Seven more people are to be questioned at a later date over doubts about their right to remain in Britain.
A Yorkshire MP said that the operation, which ended yesterday, suggested the Government had underestimated the scale of the problem.
Philip Davies, Tory MP for Shipley, said: “It probably confirms people’s worst fears that these sham weddings are being used to in fact get people into the country illegally.
“It is clear from this operation that this is a massive problem – probably even a bigger problem than the Government thought it was – and it has flagged up the extent of the abuse of the system.
“There is now no excuse for the Government to fail to bring forward some measures to tackle it.”
A sham marriage typically occurs when a non-EU national marries someone from the EU, including the UK, in an attempt to gain long-term residency and the right to work and claim benefits.
The UKBA operation followed a similar exercise in July, when 27 couples failed to attend their appointments. Sham weddings in Huddersfield, Bradford, Halifax and Wakefield have also been interrupted this year
In almost every case, it is the groom who comes from a country outside the EU. Many of the brides come from eastern European nations that have joined the EU within the last decade.
Border officials believe the weddings are being arranged by organised criminals, who can pocket hundreds of thousands of pounds from foreigners desperate to live in the UK.
The manager of UKBA’s immigration crime team in Yorkshire and the North East, Andy Radcliffe, said: “We have seen a wide range of people during the two weeks, coming from all over the world – the Indian sub-continent, Western Africa, Eastern Europe – but we want to find the organisers.
“There are people out there who are making a lot of money out of this and they are exploiting people to make this money.
“They are just saying to EU nationals ‘We’ll give you £100’. People have been given mobile phones and clothes to get married. The organisers will charge the non-EU national for their services. The going rate can be anything between £5,000 and £15,000.”
Mr Radcliffe said it was unclear how many gangs were involved in organising sham marriages but added: “We have had cases in which people have arranged five, 10 or 20 weddings.”
The Yorkshire Post revealed in March that vicars and registrars were being trained to spot bogus couples. Registrars have a legal obligation to report any suspicions, but this rule does not apply to Church of England weddings.
Mr Radcliffe said UKBA had written to the Archbishops of Canterbury and Yorks about the issue.
Comment: Page 14.