Gary Follis will take the newly-created role of head of public affairs at the UK's largest building society later this month.
Follis is a former head of public affairs at high street bank Alliance & Leicester, and became special adviser to Nick Brown on his reappointment as Government chief whip in 2008.
Following Labour's general election defeat and Ed Miliband's election as Labour leader, Brown as removed from his post and Follis moved on to become chief adviser to Winterton.
The one-time Lambeth Labour councillor will move to Nationwide at the end of the month, reporting head of external affairs Alan Oliver.
The appointment comes as the UK's largest building society reorganises its comms. Corporate affairs director Maxine Taylor is understood to have departed last month as part of a restructure that has seen corporate affairs and HR functions merged.
Graeme Hughes has become group director, HR and corporate affairs, with Oliver reporting to him.
Follis will lead a five-strong public affairs team which is currently in the process of being built.
Oliver said the appointment of Follis to a senior role at Nationwide increases the 'capacity and capability' of its public affairs operation.