Can Tesco Bank compete with high street?
Tesco Bank has apologised to customers after some savers were locked out of their accounts for the fourth day on the run.
The problems started on Monday when Tesco took control of 850,000 accounts from its former partner Royal Bank of Scotland.
The bank says all savings customers can now access their accounts online, but some will need to make changes to the settings on their internet browser.
Richard Lloyd is executive director of Which? and he told the BBC that Tesco has to invest in computer systems that work so they can compete with the other high street banks.