After her party's election victory in May 1997, she became Minister of State for Health in the House of Lords. From 1998 she was Leader of the House of Lords, playing a pivotal role in the major reform that led to the removal of most of its hereditary members. On 11 November 1999 the government's reform bill (House of Lords Act 1999) was given Royal Assent and more than 660 hereditary peers lost their right to sit and vote in the Lords.