Lara Davies will pay a £500 fine, a £15 victim surcharge and £1,410.80 in prosecution costs in line with an order by Derby Crown Court.
Davies worked for Barclays and accessed her partner's ex wife's bank account information. Her partner was involved in a dispute over the terms of a divorce and in a meeting details of eBay transactions were brought up, which raised the ex-wife's suspicions, an ICO statement said.
When Barclays investigated the issue Davies left her job, the statement said.
“The only surprise here is that – in an age where our personal information is being stored and accessed by more organisations than ever – the penalties for abusing the system are so inadequate," said Informaiton Commissioner Christopher Graham.
"High street bank staff have access to financial information on a day-to-day basis, and are expected to treat that privilege with professionalism. When that trust is abused, and the personal data they access is misused, the law is very clear, as this case has shown," he said.
The ICO has called for prison sentences to be available for breaches of the Data Protection Act.
“This case illustrates the need for more effective deterrent sentences to be available to the courts, as recommended most recently by Lord Justice Leveson," said Graham. "Unlawful access to personal information is all too easy and all too common - and these days it does not seem to have much to do with the press.”