Born in 1967, Mary grew up in Coventry where her father was a factory worker and her mother was a primary school teacher. After studying Modern Languages and then European Studies, Mary worked in Brussels before becoming a lecturer. She served as a councillor for 7 years until 2005, when she was selected as Labour’s candidate for Wakefield.
In 2005 she was first elected as MP for Wakefield after her predecessor, David Hinchliffe, retired. She was re-elected in 2017, winning 49.7% of the vote.
In 2010, Mary joined the shadow cabinet where she served as Shadow Environment Secretary, Shadow Transport Secretary, and Shadow International Development Secretary. She left the shadow cabinet in 2015.
In 2016 Mary became Chair of the Commons Environmental Audit Select Committee.