Birmingham has the second highest level of paternity tests in Britain.
More than 20,000 DNA tests, used to ascertain who a child's biological father is, are conducted across the country each year.
London accounts for more than 42 per cent of all such procedures, requested by the Child Support Agency, social services and individuals.
About 2,000 of the tests (9.84 per cent) are carried out in Birmingham. Manchester is ranked third with 7.2 per cent.
Avi Lasarow, managing director of DNA Bioscience which published the figures, said: "Paternity testing is a rapidly growing market, partly because births outside marriage have grown by more than ten per cent in the past decade. London and the West Midlands have the highest percentage of non-married people who co-habit, which could explain why London and Birmingham have topped our league table.
"Relationships between child-bearing couples are becoming more informal and temporary which means paternity issues are likely to arise more frequently."