Liam Byrne, the Labour chief secretary to the Treasury who famously left a note to the incoming coalition that Britain had "no money left", has announced he is quitting Ed Miliband's top team in order to stand for mayor of Birmingham.
England's second city is due to hold a referendum on whether to have an elected mayor in May. If the people of Birmingham vote in favour of the move, Byrne will then step down from the shadow cabinet.
A Labour Party source told the Press Association: "He has talked this over with Ed Miliband and agreed that if there was a yes vote in May, he would step down from the shadow cabinet to fight to become the first Labour Mayor of Birmingham."
Losing Byrne, seen as a member of the 'Blairite' wing of the party, would be a blow to Miliband as he is also his policy review co-ordinator.
If the referendum results in a decision to create an elected mayor, Birmingham Hodge Hill MP Byrne could face stiff opposition to secure the Labour nomination.
Former MP Sion Simon, who stood down at the 2010 general election to campaign for an elected mayor, will stand.
Another former Labour minister, Gisela Stuart, MP for Edgbaston, could also contest the position along with Sir Albert Bore, the former leader of the city's council.