Banks have been asked to turn over details of staff breaching their policies on encrypted messaging apps as UK regulators probe how the likes of WhatsApp, Signal and Telegram are used in the City.

US regulators have fined some of the sector’s biggest names including JPMorgan, Bank of America and Goldman Sachs for failing to keep tabs on potential market abuse through so-called ‘off-channel’ communications, racking up more than $2bn in penalties since investigations began three years ago.