Griffin has been a member of the Labour Party since 1988. She was a member of Unite's North West Political Committee and represented North West Constituency Labour Partys on the National Policy Forum. Griffin has also served as a Regional Organiser for the public services union, UNISON. She was Director of Communications and Research at North West Arts.[5] She was a local government councillor on Liverpool City Council in the 1990s.[2][3] As a Liverpool City Councillor, she was the lead member for Economic Development and Europe.[5]
She stood in the 2014 European Parliament election, again as a Labour Party candidate for the North West England region, and was elected as the first candidate on the winning Labour Party list.[6]
Griffin supported the Cammell Laird strikers petition to the European Parliament in 2014, believing the strikers to be the victims of a miscarriage of justice.[10][11] She supported the "Fair Pay Fortnight" in 2015, which campaigned for higher wages for workers.[12]
In 2014 Griffin called on the UK Government to correctly allocate EU funding to the North West region.[13]
Griffin advocated a Market Stability Reserve (MSR) for the EU Emissions Trading System (EU ETS). In January 2015 she led a progressive coalition to vote in rejecting proposals that she said would weaken the ETS.[16][17][18] Griffin said that the final report would have been "highly regressive and would have had an extremely negative impact on the ETS without benefiting industry in the long run."[19][20]
Griffin has written several articles on energy policy, calling for EU-wide coordination of national energy policies. In March 2015, she contributed to the tenth report of the UK Parliament's Energy and Climate Change Committee, outlining future UK energy and climate change policy requirements, with particular focus on fuel poverty.[21]
Griffin was a full member and Labour Party Spokesperson for the Industry, Research and Energy (ITRE) Committee, a substitute member on the Transport and Tourism (TRAN) Committee and was assigned to the Delegation to the EU-Russia Parliamentary Cooperation Committee and the Delegation for Relations with the People's Republic of China. In October 2014, she was appointed the S&D Shadow Rapporteur for an Opinion on the ITRE Committee about greenhouse gas emission trading.[24] She was also a member of the EU Intergroups (cross-party working groups) on Disability Rights, the Digital Agenda for Europe, Children's Rights and Well-being, LGBTI, SMEs, Tourism, Trade Union and Urban.[5]