Lawrence was selected to stand for election for Labour through an all-women shortlist, and became MP for Preseli Pembrokeshire in the 1997 election. She was a new Labour loyalist, working on environmental, rural and Welsh language issues. She was a member of the Welsh Affairs Select Committee from 1997 to 2001, and a member of the DTI Department of Trade and Industry Select Committee from 2001 until becoming a Parliamentary Private Secretary at the DTI to Jacqui Smith who was then Minister of State at the DTI. She was Chair of the Welsh Group of Labour MPs at Westminster from 2003 to 2004 and Chair of the Parliamentary All-Party Group for National Parks until leaving Westminster in 2005.