McFadden was elected as the MP for Wolverhampton South East at the 2005 general election, with a majority of 10,495, after Dennis Turner retired. In the 2006 reshuffle he was appointed as a Parliamentary Under-Secretary of State for Social Exclusion at the Cabinet Office. In the 2007 reshuffle he was promoted to Minister of State in the then newly created Department for Business, Enterprise and Regulatory Reform with responsibility for Employment Relations and Postal Affairs. In October 2008, when Lord Mandelson replaced John Hutton as Business Secretary, McFadden took on duties as his deputy in order to represent the department in the House of Commons as Mandelson is a peer and can only address the Lords. McFadden was contemporaneously appointed to the Privy Council. Following Labour's defeat in the 2010 election and the resignation of Gordon Brown, McFadden was named in interim leader Harriet Harman's shadow cabinet as Shadow Business Secretary. When Ed Miliband was elected as Labour leader in September 2010, McFadden announced his decision to stand in Labour's shadow cabinet election but was not elected. However, when he reshuffled his Shadow Cabinet in 2014, Miliband appointed him as shadow minister for Europe. In the 2015 Labour Party leadership election, he nominated Liz Kendall. He retained his post when Jeremy Corbyn became Labour leader but was sacked along with Michael Dugher in January 2016. He was sacked for what the leadership described as repeated acts of disloyalty, including when, responding to a Stop the War article on the Paris bombings, he condemned "the view that sees terrorist acts as always being a response or a reaction to what we in the west do". John McDonnell said that McFadden's remarks, expressed in a question to the Prime Minister and interpreted as an attack on Corbyn, were an example of him undermining the leader's view. McFadden was defended by Ian Austin and Chris Leslie. Jonathan Reynolds and Stephen Doughty expressed support for McFadden in their resignation letters the following day. He supported Owen Smith in the failed attempt to replace Jeremy Corbyn in the 2016 Labour leadership election. He voted in favour of the European Union Bill to trigger Article 50 and exit the European Union. He is opposed to a no deal Brexit which he believes will make the country poorer and supports a close trading relationship with the European Union. He was in favour of a second referendum to give the people a final say on leaving the European Union. He is part of Open Britain and defended Tony Blair's pro-European speech on February 2017. He is associated with the Labour right wing Labour First grouping and is a vice-chair of Labour Friends of Israel. On 9 April 2020, McFadden was appointed as Shadow Economic Secretary to the Treasury by new party leader Keir Starmer.
Personal life
McFadden and his wife, Marianna, have a son and a daughter. He is a supporter of Celtic Football Club.