Whistletree will provide a ‘safe haven’ for Northern Rock customers and receive the same benefits as those received when being managed by the government’s holding firm UKAR.
TSB confirmed it had no plans to lend new mortgages through the brand.
In November, UKAR sold £13bn of its Northern Rock book to Cerberus Capital Management, with TSB reported to be taking on a random selection of the loans, which would see 34,000 borrowers managed by the challenger bank.
TSB said borrowers managed by Whistletree would receive ‘a high level of customer service’.
Padraig Carton, customer service operations director, said: “We are delighted to welcome these customers to Whistletree from today.
“Supporting hardworking people and helping local communities right across Britain to thrive is absolutely at the heart of what TSB was set up to do. Whistletree is a natural extension of this,” he added.
“The terms and conditions of the existing loan agreements will remain unchanged. Customers transferring to Whistletree are being informed by letter this week with full details of what action, if any, they need to take.”