Companies will have their accounts closely scrutinised if they have failed to split the role of chief executive and chairman, the Association of British Insurers (ABI) warned this week.

A number of insurers have yet to accept the trade association's guidelines for corporate governance.

About 20 letters were sent to major companies last autumn, asking them why the two positions were held by one person. The ABI said splitting the jobs ensured accountability.

Peter Montagnon, head of investment affairs at the ABI, said: “There were a number of companies where the roles were still combined and we invited them to think very carefully about why they were doing this and invited them to explain themselves.

“Three to four have now announced changes and others have promised changes are in the pipeline.

“Some have had particular reasons why they thought it was appropriate to do so, but most have come back with replies after discussions of the board.”

Powergen and JJB Sports have announced the roles will no longer be combined and other firms look set to put the suggestions into practice.

Montagnon added the ABI would keep a close eye on those that refuse to implement the suggestions and would examine their annual reports carefully.

“We represent a huge stake in these companies so we have people whose views should be listened to,” he said. “We aren't ordering them about but are exercising our opinions and encouraging them to conform to a better practice.”

He added that the ABI would not hesitate to write more letters with suggestions.

He said: “It is our intention to be active in the pursuit of good corporate governance.”