In January 2016, Lewell-Buck became shadow minister for devolution and local government in Jeremy Corbyn's frontbench reshuffle. On 29 June 2016, she announced her resignation from the post, commenting that she was "heartbroken at the state of the [Labour] Party". This was a reference to a string of shadow cabinet resignations during the summer leadership crisis. She later supported Owen Smith in the failed attempt to replace Jeremy Corbyn in the 2016 Labour Party leadership election.
