[1] In the 2015 United Kingdom general election, Greene stood for the UK Parliament as the Conservative candidate for North Ayrshire and Arran where he came third.

[3][4] In September 2019 it was announced he had been selected to stand for the 2021 Scottish Parliamentary election for the Cunninghame North seat.

Greene was appointed as Shadow Cabinet Secretary for Justice in the current term of Parliament, later replaced by Russell Findlay in a reshuffle.

Previously he held the role of Shadow Cabinet Secretary for Transport, Infrastructure and Connectivity.

Greene initially expressed an interest in standing for the 2020 Scottish Conservative & Unionist Party Leadership Election, but announced in January 2020 that he was dropping-out to support incumbent acting-leader Jackson Carlaw who was later replaced by Douglas Ross.