Commonwealth nations on Friday agreed to scrap centuries-old laws barring first-born daughters or anyone married to a Roman Catholic from inheriting the British throne. British Prime Minister David Cameron said the agreement, backed by the 16 nations which have Queen Elizabeth II as head of state, represented a \"historic moment\" for the monarchy. He said the changes, which have to be formally approved by the affected nations, would sweep aside outdated rules that \"just don\'t make sense to us any more\". \"We will end the male primogeniture rule so that in future the order of succession should be determined simply by the order of birth,\" Cameron told reporters at a meeting of Commonwealth leaders in Perth. \"We have agreed to scrap the rule which says that no one that marries a Roman Catholic can become monarch.\" Cameron has the political support to make the changes in Britain but required the agreement of the 15 other Commonwealth realms, including Canada, Australia, New Zealand and smaller nations in the Caribbean and the Pacific. There has been a reluctance to press the issue in the past due to the legal complexities and concern that tinkering with the rules may encourage republican movements. But the debate was intensified by the wedding in April of William, the second in line to the throne, while the celebrations for Queen Elizabeth\'s 60 years as monarch next year may also be a chance to rally support. \"Put simply, if the Duke and Duchess of Cambridge were to have a little girl, that girl would one day be our queen,\" he said, referring to William and his wife Catherine. Cameron said the monarch would still have to be Protestant because he or she heads the Church of England. \"But it is simply wrong that they should be denied the chance to marry a Catholic of they wish to do so, after all they\'re already quite free to marry someone of any other faith,\" he said. He said an international group would be established to implement the changes at the same time across all 16 nations.