All 144 matches in the group phase of this season's UEFA Europa League will be officiated by six match officials. In an experiment endorsed by the IFAB (International Football Association Board), the customary four-man team of referee, two assistant referees and fourth official will be supplemented with two additional assistant referees who will take up positions alongside each goal.

At its 123rd Annual General Meeting in Newcastle, Northern Ireland on 28 February this year, the IFAB, composed of representatives from the four British football associations and FIFA, gave its consent for the experiment initiated in selected UEFA European Under-19 youth qualifying tournaments in 2008 to continue at professional level. The choice of the new UEFA Europa League as the competition for this next phase was confirmed in May.

In essence, the additional assistant referees will provide two extra pairs of eyes to monitor the game and ensure that the Laws of the Game are upheld, informing the referee of incidents of any kind that he may otherwise have missed, particularly in key areas of the field like the penalty area and its surroundings. The referee will remain in sole charge of the match and the only match official with decision-making powers.

The additional assistant referees will be positioned on the opposite side of the goal from the assistant referee - to the left when viewed from the centre circle. Using a radio communication system to relay their recommendations to the referee but without flags, the additional assistant referees will generally remain behind the goal line but may enter the penalty area when play moves towards the other end of the pitch so as to keep up with the action.

Given the potentially crucial importance of their interventions on the course of a game, referees from FIFA's current international list or from the highest category at national level (aged under 45 on 1 January 2009) will fill the additional assistant referee role. In keeping with existing policy, they will share the same nationality as the four other members of the UEFA Europa League refereeing team to which they are appointed.

A briefing for referees and referee observers was held at UEFA's headquarters in Nyon, Switzerland this week under the auspices of the guardians of the Laws of the Game, the IFAB. The 48 referees and 48 observers appointed for the 2009/10 UEFA Europa League group stage were given extensive instructions and guidelines by refereeing instructors in preparation for the launch of the experiment when group matches kick off on 17 September.

Technical experts appointed by the IFAB will monitor developments throughout in order to assess the impact the two additional assistant referees have on the game and to determine whether they enhance the officials' control of the match. The conclusions will later be presented to the IFAB for consideration.

About the IFAB
Founded in 1886, the IFAB is composed of The Football Association (England), The Scottish Football Association, The Football Association of Wales, The Irish Football Association (Northern Ireland) and FIFA, and has historically held the position as guardian of the Laws of the Game. Each British association has one vote apiece, while FIFA, which represents its 204 other member associations, has four. A three-quarter majority is required for any proposal to be passed.