Gordon Brown is backing electoral reform calling for a referendum on replacing the current "first-past-the-post" voting system with an "alternative vote" system, or, instant runoff voting (IRV) to give the American English term for the system. Under an AV system, voters are asked to rank candidates by preference rather than putting a cross by a single name anyone getting more than 50% in the first round is elected. If that doesn't happen during the first round, the candidate with the fewest votes is eliminated and their second choices allocated to the remaining candidates. This process perpetuates until a winner is produced. This electoral system is currently used for elections to the Australian House of Representatives.

There are critics and supporters of the AV system, both with arguments to cite. Supporters say the alternative vote retains the same constituencies and so that MPs won’t loose their constituency links. It prevents MPs being elected on a minority of the vote. In 2005, only 34% of British MPs were elected by more then 50% of the votes in their constituencies, ensuring all MPs would have the support of a majority of their constituents. Another advantage supporters will voice is that extreme parties would be unlikely to gain support by AV and coalition governments would be no more likely to arise than they are under First-Past-The-Post. Critics will cite that an AV system does very little to give a voice to those who have been traditionally under-represented in parliament.  Also the  AV system will do nothing to  produce a proportional parliament. Finally AV is prone to varying degrees of 'Donkey voting', where voters rank candidates randomly, not knowing enough about all the candidates to make an informed decision.

The previous PM, Tony Blair also advocated proposals for electoral reform when plans were proposed by the late, Lib Dem, Lord Jenkins in a 1998 review, saying Lord Jenkins "makes a well-argued and powerful case for the system it recommends” This however, was for a slightly different system to the AV system. Jenkins argued for a mixed system known as Alternative Vote Plus. However, Jenkins became disillusioned and irritated with Tony Blair for refusing to adopt his plans for electoral reform despite a commitment to a referendum on electoral reform in Labours 1997 manifesto.