The role of the external auditor must be overhauled, according to a survey by the Institute of Internal Auditors.

It found that half of internal auditors wanted governance practices changed to provide greater auditor independence.

They called for the appointment of stronger non-executive directors from a wider range of backgrounds and more rigorous controls over the consulting work done by external auditors.

Institute chief executive Gail Easterbrook said: "They feel that two of the major governance relationships - that between the external auditors and the audited company and between the non-executives and the board - are not working as effectively as they should."