The Equality and Human Rights Commission has published guidance in relation to the equality framework for board appointments. It  clarifies that an individual cannot be given preference or selected for appointment simply because  of his or her gender but companies may take positive action to promote participation by women (and  persons with other protected characteristics) if the participation in a particular activity - such  as holding a directorship in a particular company - is particularly low amongst persons  sharing that protected characteristic and the aim of the positive action is to enable or encourage persons with that protected  characteristic to take up that activity.

See here for details.