Skipton Building Society is selling a £250m mortgage book originating from its Amber Homeloans brand.
Skipton has appointed Morgan Stanley to drum up appetite for the loan book, according to Sky News.
A number of bidders have reportedly expressed an interest, and the sale process is already underway.
A Skipton spokesman says: “Our position is we don’t comment on rumour or speculation about corporate activities.”
The lender was last in the news at the end of January when it announced it was cutting rates on selected buy-to-let and Help to Buy products by up to 0.44 percentage points.