In the lead-up to the 2005 federal election, as a reaction to Schröder's Agenda 2010 reforms, Lafontaine co-founded the left-wing party Labour and Social Justice – The Electoral Alternative.

Lafontaine resigned from the Left Party on 17 March 2022 because it was no longer an "alternative to the politics of social insecurity and inequality," he said.

He spent his childhood living with his mother, Katharina (née Ferner), and his twin brother, Hans, in Dillingen.

[5] Lafontaine rose to prominence locally as mayor of Saarbrücken and became more widely known as a critic of chancellor Helmut Schmidt's support for the NATO plan to deploy Pershing II missiles in Germany.

After the SPD's unexpectedly clear victory at the polls in September 1998, he was appointed Federal Minister of Finance in the first government of Gerhard Schröder.

[7] Lafontaine joined the WASG on 18 June 2005 and was selected to head their list for the 2005 Federal Election in North Rhine-Westphalia on the same day.

[12][13] In the late 1980s and early 1990s, he caused controversy among his left-wing base with a plea for pro-business policies and a call for the reduction of immigrants and asylum-seekers.

He said afterwards that he had misspoken, but in an article published in Die Welt, a group of prominent German writers accused him of deliberately appealing to xenophobic and far-right voters.

[14] Lafontaine lives in a manor-like house, commonly known as the "palace of social justice" (Palast der sozialen Gerechtigkeit).

[15] When asked by the Frankfurter Allgemeine Zeitung about whether this could be in conflict with his socialist ideas, Lafontaine said politicians of the left do not have to be poor, but they have to fight against poverty.

[16] In a column published by the same newspaper Lafontaine criticized the expansion of wind power, citing the alleged "destruction of the German Cultural landscape" as a cause for his objection.

[17] The Alliance 90/The Greens top candidate Barbara Meyer-Gluche pushed back at this stance and accused Lafontaine of "irrational fearmongering".