Monzo, which operates a smartphone-only model, was named the most popular bank with a customer score of 86%, according to Which?. It finished above First Direct, which scored 85%.

Meanwhile, both banks achieved five stars for customer service.

Nationwide Building Society claimed third spot with a customer score of 79%, while Metro Bank came fourth with 76%.

The findings, which were based on survey results from over 4,000 members of the public, underscore the growing popularity of challenger banks – with Monzo and Metro Bank claiming two of the four top spots.

The survey results also suggest that customers do not find Monzo’s smartphone-only model restrictive.

Which?’s survey showed high dissatisfaction amongst TSB’s customers, following a string of IT meltdowns which left customers locked out of their accounts. It fell from fourth position in the previous survey in February of this year to joint-bottom position with Bank of Ireland.

Around 56% of TSB customers said they had experienced technical issues over the past 12 months, with the bank scoring poorly on customer service, telephone and online banking and complaint handling. It was awarded only two out of five stars in these categories.

Royal Bank of Scotland also scored poorly with a 60% customer satisfaction, just ahead of TSB and Bank of Ireland.

“Our research shows a clear gap between the best and worst providers and should act as a catalyst for customers unhappy with their service to switch banks – as it’s never been easier,” Gareth Shaw of Which? said.

Shaw also welcomed the new-found dominance of challenger banks, which shows that innovation and modern ideas are shaking up the banking sector.