Investment bankers and traders in Britain will have their mobile phone conversations recorded in the latest step by the country’s financial regulator to crack down on insider trading and market abuse.

The Financial Services Authority, Britain’s financial watchdog, said Thursday that under new rules, effective next November, all financial services firms will be required to record any relevant communication by employees on their work cellphones.

Companies would also be responsible for discouraging employees from taking client orders or discussing and arranging transactions on their private cellphones, where conversations cannot be recorded.

The new rule makes Britain the only country in Europe to explicitly require the taping of conversations on business cellphones, according to the F.S.A. Rules in other European countries merely require companies to ensure that all relevant conversations are recorded...