portfolios, calming internal tensions. During the 1998 Waitangi Day celebrations, Clark was prevented from speaking on the marae by activist Titewhai Harawira in protest over Clark's being allowed to speak in direct contradiction of traditional Māori protocol. The ensuing argument saw Clark being reduced to tears on national television. In 1999, Clark was involved in a defamation case in the High Court of New Zealand with Auckland orthopaedic surgeon Joe Brownlee, resulting in Clark's making an unreserved apology. The case centered on a press statement issued by Clark criticising Brownlee, triggered by a constituent's complaint over the outcome of a hip replacement. Clark admitted the criticism was unjustified in that the complication suffered by her constituent was rare, unforeseen and unavoidable. Prime Minister (1999–2008) Under Clark's leadership, Labour became the largest party in parliament from 1999 to 2008. Clark became the second woman to serve as Prime Minister of New Zealand, and the first to have won office at an election. She also served as the Minister for Arts, Culture and Heritage throughout her premiership. She had additional ministerial responsibility for the New Zealand Security Intelligence Service (NZSIS) and for Ministerial Services. During her period in office, women held a number of prominent elected and appointed offices in New Zealand, such as the Governor-General, Speaker of the House of Representatives and Chief Justice—these major offices of state were simultaneously occupied by women between March 2005 and August 2006. As a female head of government, Clark was a member of the Council of Women World Leaders. Clark entered office just three years after the adoption of the Mixed Member Proportional (MMP) voting system, which had produced an unstable National-led government under Bolger and Shipley. Clark negotiated the formation of successive coalition governments. Political scientist Bryce Edwards identified Clark's ability to lead stable governments as her most significant achievement, arguing that her ability to work with a variety of coalition partners—including the Alliance, Jim Anderton's Progressive Party, Green, United Future and New Zealand First—consolidated public support for MMP. Clark's particular interests included social policy and international affairs. A strong supporter of nuclear disarmament, Clark pursued a policy of peace-making within the Pacific region. She set herself the task of making New Zealand the first ecologically sustainable nation, describing this as "central to New Zealand's unique national identity". Her government's major policy achievements include the Working for Families package, increasing the minimum wage