Migrants are seeking to marry "sham brides" who are pregnant with another man's child in a bid to exploit human rights laws and remain in Britain.
In a major immigration scam, non-Europeans who would be unlikely to gain a visa to live or work in the UK are also trying to wed women who already have children.
Under the Human Rights Act, they can then claim that kicking them out would breach their safeguards to a family life, despite not being the father of the children involved.
And an immigration watchdog report has found the system is suffering significant abuse at the hands of these men from outside Europe. Yesterday, Independent Chief Inspector of Borders and Immigration David Bolt said the trend had emerged as part of the "sham marriages" scandal.
Tens of thousands of people apply to stay in the UK each year on the basis of bogus marriages. Criminal gangs often charge thousands of pounds to set up men - who are desperate to illegally gain the right to remain in the UK - with vulnerable women who have been trafficked.