Rival factions in Northern Ireland's unity government are accusing each other of bias after a policeman who oversaw the arrest of Sinn Fein party leader Gerry Adams was promoted to the force's second-highest post.

Adams spent five days in custody in May over his alleged role in the 1972 Irish Republican Army abduction, killing and secret burial of a widowed 38-year-old mother of 10 children. IRA veterans on audiotapes accused Adams of ordering the killing. Adams, who denied involvement, was released without charge.

Sinn Fein, the main Catholic-backed party, resigned from the selection committee after others supported Tuesday's promotion of Drew Harris to deputy chief constable. Harris was director of the Crime Operations Department responsible for Adams' arrest.

Protestants accused Sinn Fein of undermining public support for law and order.