NatWest has blocked its staff from using WhatsApp, Facebook Messenger and other messaging services on their company devices.
The bank’s guidance has already told employees they should use only certain channels of communication.
But it has now blocked access to a number of messaging services on work devices.
Approved channels of communication must have retrievable records, according to NatWest’s policies.
“Like many organisations, we only permit the use of approved channels for communicating about business matters, whether internally or externally,” a spokesperson for NatWest Group said.
Companies are increasingly seeking to address problems with off-channel communications.
Fears have been raised that the use of WhatsApp, Skype, Facebook Messenger and other channels can reduce the possibility of scrutiny of a company or employee’s practices.
The bank’s move came into effect on 6 November, in an attempt to prevent the possibility of off-channel services being used.
In August, the Financial Conduct Authority said it would begin investigating how staff within City firms use encrypted messaging services, Financial News reported.
In recent years, US banks have been fined billions for permitting the use of apps such as WhatsApp, Signal and Telegram to communicate about work.
The US Securities and Exchange Commission has reportedly received $2.8bn (£2.2bn) in fines since 2021 from companies including Wells Fargo and BNP Paribas.
Last August, Ofgem fined Morgan Stanley for “not recording and retaining electronic communications between January 2018 and March 2020.
The communications were made on “privately owned phones via WhatsApp, which discussed energy market transactions”, and led to a £5.41m fine.
It was the first ever fine in Britain under legal requirements to retain electronic communications relating to wholesale energy products, Ofgem said.
At the time, regulatory director of enforcement and emerging Issues at Ofgem Cathryn Scott said: “This fine sends a strong message to market participants that they must comply with all REMIT rules or face enforcement action.”