Digital bank N26 has been ordered to improve its staffing and engineering teams by Germany's financial regulator. The intervention comes after a customer complained that €80,000 (£68,000) was stolen from their account.

The mobile bank is one of Europe’s leading financial technology start-ups, similar to British rivals Monzo and Revolut, and is rapidly expanding around the world. It launched its online banking service to UK customers in October and now has around 2.5m users globally.

Concerns have been raised over the ability of banks and customers to contact the financial technology start-up after it was reported that the bank took days to respond to a fraud issue.

The German banking regulator BaFin has also ordered Berlin-headquartered N26 to fix issues around its staffing and engineering, German newspaper Handelsblatt reported. The company risks having a cap placed on the deposits it is able to take if it fails to respond to the regulator’s concerns.

N26 does not have a banking licence in the UK, and instead has "passported" its German banking licence over in order to operate here. Any restrictions placed on its German licence would also apply to other countries that it has passported its licence to.

Chief executive Valentin Stalf told Handelsblatt his business had previously failed to hire enough staff.