City traders should be forced to take a two-week holiday to protect firms against the risks presented by rogue traders.
The Financial Services Authority (FSA) said that a continuous two-week break would help prevent a repeat of the Societé Generale affair where rogue trader Jerome Kerviel lost £3.7bn.
The holiday would allow other colleagues to inspect the books and ensure everything was in order.
Kerviel reportedly refused to take holiday despite being ordered to do so.
The watchdog said it had met with British banks and had urged them to remain vigilant on unauthorised trading.
Sally Dewar, managing director of wholesale and institutional markets at the FSA, said: “We are encouraged that many firms in London with significant trading activities are working to satisfy themselves that their basic controls and governance surrounding trading, risk management and settlement are effective.”
City firms should also tighten up computer security and ensure back-office staff had sufficient control of traders, the FSA recommended.