Marlin specialises in collecting from wealthy debtors, with “litigation quality” arrears that can be recouped through the courts.
Duke Street partner Miles Cresswell-Turner said: “Marlin has the potential, with funding and operational help from Duke Street, to become a clear category-killer among litigation-focused debt purchasers.
“The debt purchase sector is set to recover sharply in the next two to three years, so this investment is an opportunity to build a focused platform with strong upside characteristics.”
Duke Street also acquired payment provider Payzone earlier this year.
Last year creditors outsourced £13.1bn of delinquent debt to third party collectors, including £2.7bn sold to debt purchasers.