Royal & Sunalliance (RSA) has suspended up to 41 staff after they exchanged what has been described as a lewd, smutty and risqué Bart Simpson email.

Newspaper reports have said up to 100 staff are now being quizzed over the email, in an investigation that RSA UK corporate communications head Paul Atkinson admitted centred on the Liverpool office.

Reports also said the email, which contained a doctored image of the cartoon character, had been discovered after it was accidentally sent to an RSA director, but Atkinson denied this was true.

Atkinson would not comment on the number of staff involved or the length of the investigation but said staff had been warned that RSA's policy on internet use would be strictly administered.

“We're not going into detail on how the investigation is going but it's fair to say the Liverpool office is a focus,” he said.

“We've issued a company policy on use and misuse of email in the past and warned staff that breaches of the policy would be taken seriously, as we are doing.”

The scandal follows the recent suspension of five staff at law firm Norton Rose, after a woman's sexually explicit email to her boyfriend at the firm was forwarded to an estimated two million people around the world.