Abbey National chief executive Luqman Arnold and director of product strategy Gary Hockey-Morley, who is currently looking after branding and marketing, oversaw the appointment.
Last week, several agencies, believed to include the incumbent and BMP DDB as well as TBWA were given just 48 hours to put together a presentation. TBWA was awarded the business almost immediately.
Arnold said: "We now have a new management team, a new strategy and have taken the opportunity to take a fresh look at the market.
"TBWA stood out with a range of challenging ideas and will bring an impetus to our goal to become the UK's biggest provider of personal financial services."
The UK's sixth-biggest bank recently announced losses of almost £1bn, one of the worst returns in UK banking history. Hockey-Morley said the review was completed quickly because "there are a lot of things that need doing to turn around the organisation".
Last month, Arnold implemented a management shake-up at Abbey. Top marketer Janet Connor moved to a new role overseeing customer sales. Hockey-Morley also confirmed that the bank is looking externally for a head of customer proposition to have overall charge for marketing, though he stressed Arnold will be very involved in marketing decisions.
TBWA will work closely with Wolff Olins, which was recently hired to review Abbey National's brand strategy (Marketing, March 6).
Euro RSCG created campaigns for Abbey including 'Life's complicated enough' with comedian Alan Davies and more recent work featuring former EastEnders star Martin Kemp.
TBWA already counts The One Account (formerly Virgin One) as a client, but said there would be no conflict.