Alan Boswell Insurance Brokers is suing a former employee who copied a client database and then persuaded clients to join a rival firm, a High Court writ says.
Account executive Richard Beevor said he wanted a lifestyle change and to leave the industry after more than 10 years at Alan Boswell, the court papers say.
Beevor handed in his notice on 9 May this year, and was put on gardening leave until 1 August.
But during that time he started working for Norwich-based Drayton Insurance Services and used a database copied from Alan Boswell to contact old clients and persuade them to move over, it is claimed.
Because Beevor was on gardening leave at the time, he was still employed by Alan Boswell when he joined Drayton, the writ says.
Alan Boswell took out an injunction on July 6 demanding that Beevor hand over old client lists or any other documents.
Alan Boswell will only know the full details of any losses once Beevor has done so, the writ says.
Beevor dealt with around 333 clients that brought in £400,000 of commission a year, it is alleged.
Beevor and Alan Boswell declined to comment.