Jonathan was elected Member of Parliament for Leicester South at a by-election in May 2011.
In November 2021,he was appointed Shadow Secretary for Work and Pensions, having previously been Labour’s longest running Shadow Secretary of State for Health and Social Care. He has also served as Shadow Minister without Portfolio and Shadow Cabinet Office Minister and is a Policy Fellow at the Centre for Science and Policy, University of Cambridge.

Before becoming an MP, Jonathan worked in the Treasury as a special advisor to Gordon Brown when he was Chancellor, and continued to work for Gordon Brown when he became Prime Minister.

In 2016, Jon made one of the most difficult speeches of his life when he spoke publicly about his own experience of watching his father’s struggle with alcohol. Following this, he was inundated by people getting in touch. So despite feeling guilty after speaking publicly, and feeling that he may be betraying his father, he continues to raise awareness.