[5] Miller contested the newly-created Ward 9 councillor's seat after the amalgamation of the City of Hamilton in 2000, but lost to the last mayor of Stoney Creek, Anne Bain.

[7] In April 2008, Miller introduced a private member's bill that proposed to create a severance fund for workers who were owed money when their companies closed.

Though he was a member of the NDP, Miller introduced the bill jointly with Niagara West-Glanbrook MPP (and Ontario PC Party leader) Tim Hudak.

[12][13] Miller served as the party's critic for Tourism, Culture and Sport and for the 2015 Pan and Parapan American Games.

[14] In 2016, Miller advanced a bill that would look at the costs of living in various economic regions in Ontario, provide education around social assistance rates, and examine unsafe working conditions in the province.

In 2018, questions were raised about Miller's future in Ontario provincial politics after a series of allegations of bullying, racist remarks, and abuse of office resources.

A statement to the Human Rights Tribunal of Ontario claimed Miller regularly displayed sexist, racist and homophobic behaviour.

[20][21] In Ontario's 2018 election, Miller was able to claim his 4th victory in his Hamilton East-Stoney Creek Riding with more than 51 percent of the overall vote.

The $1.3-million breach of contract claim against the NDP, Leader Andrea Horwath and two party officials, filed in a Hamilton court, alleges the Ontario NDP, Horwath and officials Lucy Watson and Michael Balagus, conspired to remove Miller from the caucus by knowingly using a false allegation.