TSB provided £5.8bn of new mortgage advances in the nine months to 30 September 2017, up 17.5% on the time period last year.
The bank saw management profit before tax fall slightly by 1.3% to £147.3m over the period.
Paul Pester, chief executive officer at TSB, said: “When we launched TSB in 2013, we set out to break the stranglehold of the big five banks and bring a different sort of banking to the UK.
“Looking forward, our new, state-of-the-art banking platform will be transformational as we continue on our mission to bring more competition to UK banking – both for consumers and local businesses.
“The new platform will position TSB well to compete for one of the grants from the Capability and Innovation Fund recently announced by the government.
“Breaking the stranglehold of the big five banks remains top of our agenda and we’ll continue to work closely with the government, policymakers and regulators in an attempt to bring the full force of competition to bear on the UK banking market – and ultimately make banking better for all UK consumers.”
The Mortgage Enhancement Portfolio, a £3.4bn residential mortgage loan book created in February 2014, generated £61.7m management profit before tax which is a yearly increase of £25.6m.
These results come as TSB is set to become the first major bank in the UK to have designed and built a new banking platform for the digital age.