Prior to becoming an MEP, Dance worked for the development charity ActionAid UK, working on campaigns for structural changes to alleviate poverty and hunger around the world. He worked on a long-running campaign against tax avoidance by large multi-national companies. Before joining ActionAid UK he worked for a small communications company working with clients in the public, private and voluntary sector on a range of campaigns. Before this he worked as an advisor to the Secretary of State for Northern Ireland between 2007 and 2009, when the final parts of devolution as part of the 1998 Good Friday Agreement – policing and criminal justice powers – were being delivered by the Labour Government.
Dance was elected to the European Parliament in 2014. On entering the European Parliament, he was appointed to the European Parliament Committee on the Environment, Public Health and Food Safety, responsible for a wide range of policy areas including air and water pollution, waste management, and climate change. He is a Vice-Chair of the committee and has chaired committee meetings, joint meetings with other committees such as AGRI, as well as formal trilogue meeting on the Drinking Water Directive. He also sat on the European Parliament Committee on Development, overseeing the spending commitments and priorities of the EU's development budget. Dance was appointed as a shadow rapporteur for the revision of the National Emissions Ceiling Directive, which aims to improve levels of air quality by regulating the emissions of harmful pollutants. This is particularly important issue for London, where over 3,000 people are dying prematurely each year as a result of exposure to poor air quality. He became the S&D spokesperson on air quality following his appointment as a Shadow Rapporteur on the NECD. Following the "Dieselgate" scandal involving the use of so-called cheat devices in Volkswagen cars the European Parliament voted to set up a committee of inquiry to look into the scandal, the extent to which EU institutions acted on knowledge of the presence of software to limit emission abatement technology in the automotive industry and to provide recommendations on how to prevent a similar scandal in the future. He was appointed by his group colleagues in the Committee to be the Co-Ordinator for the S&D group on the committee, meaning he chairs the delegation of S&D MEPs in the committee and is the group's spokesperson on the committee. In the 2014 Parliament, Dance was appointed as the Rapporteur for the DEVE Committee for delivering the UN's Sustainable Development Goals. The "Dance Report" provided the European Parliament with its first blueprint for delivering the SDGs across all areas of the Parliament's work as well as holding the other EU institutions to account on their programmes for delivering the SDGs. He is also a shadow rapporteur on a proposal for an integrated approach to tackle the link between conflict and the trade of minerals extracted from affected areas. He supported Owen Smith in the 2016 Labour Party leadership election. In February 2017, he held up a placard directed at UKIP MEP Nigel Farage, saying "He's lying to you" when Farage made a speech to the EU Parliament defending Donald Trump's 90-day ban on immigrants from seven countries entering the United States. UKIP MEP Bill Etheridge consequently wrote to Antonio Tajani to complain about the incident, claiming that it was "disgusting behaviour" and "pathetic". Dance later wrote to Tajani, saying he apologised for the method, but not the message. Dance has been a consistent supporter of the EU and the need for multilateralism to combat extremism and climate change, and has been a vociferous opponent of Brexit.
