He left the NUS in 1984 to work in the East End of London and in 1986 was elected as a Labour member, on Hackney London Borough Council. In 1990 he became Deputy Leader of the Council. Sheppard unsuccessfully contested Bury St Edmunds at the 1992 United Kingdom general election for the Labour Party, polling 14,767 votes and 23.6% of the vote. He moved back to Scotland and settled in Edinburgh, taking up a position with the District Council. In 1994 he was appointed Assistant General Secretary of Scottish Labour under John Smith. In 1997 he was made redundant from this role due to internal policy disagreements. He ceased to renew his Labour Party membership in 2003, stating: "I joined the Labour Party in 1979, just before my 21st birthday. Now 25 years later I've finally got around to cancelling the direct debit. I can no longer bring myself to vote Labour. My outlook has barely changed, but clearly the Labour Party has. I can no longer believe the Labour Party is likely to change the world very much, or at least not in a direction I would like". In 2012 he became the Edinburgh South organiser of the Yes Scotland campaign, but joined the SNP only in 2014 after the 2014 Scottish independence referendum. He was selected as candidate for the Edinburgh East constituency and polled 23,188 and 49.2% of the vote, securing election with a majority of 9,106 and defeating incumbent Labour MP Sheila Gilmore. In October 2015 Tommy was elected to the SNP's National Executive Committee. In March 2016 the Parliamentary Standards Committee announced that Mr Sheppard was under investigation for non-declaratory incomes. Last year his own company Salt n' Sauce Promotions Limited shareholder Funds had proven greater than Sheppard had claimed. He was reprimanded in the press by chairman Lord Bew, who called on reforms to be made to the scrutiny process of MPs earnings. At present such reported errors could be dismissed as merely "administrative" omissions. The details included thresholds governing how much ownership and share of control over companies must be over 15%. Sheppard is a staunch republican, and during the wedding of Prince William and Kate Middleton, he remarked "off with their heads", prompting some criticism. Sheppard is an atheist and a humanist, and was elected Vice Chair of the All-Party Parliamentary Humanist Group in 2017. He held his Edinburgh East seat in the 2017 United Kingdom general election, albeit with a slightly reduced majority. During the election, he urged the Scottish Greens to step down from contesting marginal seats where the pro-independence vote might be split. Following the 2017 election, which he described as a "major wake-up call" for the SNP, Sheppard encouraged First MinisterNicola Sturgeon to abandon plans for a second Scottish independence referendum before Brexit. He suggested the cause of Scottish independence would be served best if Sturgeon offered Scotland a vote on a future relationship with the European Union after Brexit and only once Scotland had become independent. In November 2017 he claimed that Scotland still had a mandate for a second independence referendum and that the Conservatives were wrong to think that the loss in SNP seats in the snap general election had caused a delay in the timetable for a second vote. He has expressed admiration for the 18th century Scottish reformer and radical Thomas Muir, linking Muir's politics and life to the modern Scottish independence movement. In 2018, he was widely considered one of the possible contenders for the 2018 Scottish National Party depute leadership election after having stood in the previous 2016 depute leadership election, but ruled himself out.
Comedy
Sheppard is a co-founder and former manager and promoter of The Stand Comedy Clubs in Edinburgh, Glasgow and Newcastle.