Metro Bank has sold its book of prime mortgages to NatWest in a £3.13bn deal.
The deal will see more than 13,000 customers transferred from Metro Bank to Natwest.
The book has a weighted average current loan-to-value ratio of around 60%.
Alison Rose, Natwest chief executive, said: “Growing our mortgage book is an important strategic priority as we build a bank that delivers sustainable returns for shareholders.
“The addition of this loan book will supplement the strong organic growth that we continue to achieve.”
The agreement will help Metro Bank boost its capital amidst the ongoing coronavirus pandemic. Back in October the bank warned that its capital levels were below buffers expected by regulators.
In August Metro Bank bought peer-to-peer lender RateSetter as it tries to improve revenues. Last week RateSetter sold its development finance arm to challenger bank Shawbrook.