Metro Bank has taken top spot in an official survey of customers' satisfaction with their banks, with the Royal Bank of Scotland ranked bottom.
Despite Metro's share price having been hit, in part, by errors in the way it accounted for some of its lending, the bank overtook First Direct to go top.
Some 83% of its personal customers said they would recommend the bank to their family and friends.
The rankings are published every six months by the UK's competition body.
Banks must prominently display the results in branches, on websites and apps, with the aim to encourage competition on customer service.
The rankings are drawn from the views of 16,000 people (1,000 from each bank), who were asked how likely they would be to recommend their account provider to friends and family.
For personal banking, Metro Bank - which started operating in the UK in 2010 - was the most popular.
It has had a relatively tough few months in terms of its share price, but was second in the customer satisfaction ratings six months ago and has now taken top spot.
A Metro Bank spokesman said: "Our offering is simple. We believe in providing the very best in service and convenience for both consumers and businesses, and this latest set of results speaks for itself."
It has switched positions from six months ago with First Direct, with the Nationwide Building Society maintaining its position in third.
The Royal Bank of Scotland was bottom of the 16 banks on the list. It scored poorly on services in branches.
On the day that its parent company RBS announced a doubling in annual profits, the survey revealed that fewer than half (47%) of Royal Bank of Scotland personal current account customers said they would recommend the bank.
Among the various categories, TSB - which suffered a major IT failure that led to the departure of its chief executive last year - finished bottom of online and mobile banking services. Clydesdale Bank was bottom on the ranking of overdraft services. HSBC-owned First Direct, which has no branches, was top of both these categories.
Nearly 20,000 small businesses were also asked about customer service at banks, resulting in a ranking of 14 banks.
Swedish import Handelsbanken was ranked top with an 85% satisfaction rating, with a particularly strong showing in the relationship and account management category (91%).
Metro Bank was second and Santander third. TSB was bottom of the 14.
Andrea Coscelli, chief executive of the Competition and Markets Authority, which published the results, said: "We introduced this survey last August so that people can see exactly how well banks are treating their customers.
"If people are unhappy with the customer service they are currently getting, I would encourage them to look at the results and think about switching to a better performing bank."