Civil service commissioner Baroness Prasher will today outline a new recruitment code, in a bid to retain Whitehall's independence.

Under current rules governing the top 160 civil service appointments, ministers are given a choice of two or three candidates when selection is made internally, while external appointments are made through a selection panel, offering ministers only the "best" candidate.

Under the changes, ministers will be able to refer the matter back to the selection panel if they feel unable to appoint the lead candidate.