JOIN USParminder Singh from India and Irina Iljina from Latvia, both 22-year-old, pleaded guilty to charges of conspiracy to breach immigration laws, The Times reported.
They were due to marry on December 17. But the night before the wedding, suspicious officials found Iljina at home in bed with her real boyfriend.
Singh and Iljina, both from Peterborugh, also admitted a perjury charge at Peterborough Crown Court on Friday, the report said.
The court heard that the UK Border Agency was notified when they registered their intention to marry on November 30.
The registrar contacted officials as the couple seemed to know little about each other.
"It's reasonable to say the compromising circumstances in which Iljina was arrested cast further serious doubt on what was an already dubious relationship," Sam Bullimore, of the UK Border Agency, said, adding, "Where we uncover suspicious marriages, we will challenge them and prosecute where appropriate."
The pair will be sentenced on January 28. Last summer, an operation resulted in 118 arrests, including a vicar who was jailed for fixing more than 300 ceremonies.