Nick Brown has been appointed as Labour's new chief whip as Jeremy Corbyn began reshuffling his top team following his re-election as leader.
Mr Brown, a long time ally of former leader Gordon Brown, replaces Rosie Winterton.
In a statement, Mr Corbyn welcomed Mr Brown's agreement to take on the role and paid tribute to Ms Winterton.
Mr Brown said: "I hope that I can bring experience and play a constructive role in providing the strongest possible opposition to this Tory Government."
The new chief whip held the same position when Mr Brown was prime minister, after serving in several government roles under Tony Blair.
Ms Winterton said: "It has been an honour to have served as Labour's chief whip for the past six years under three different leaders. I would like to thank the whips and the Parliamentary Labour Party for the support they have given me. I wish Nick Brown every success in his new role."
A Labour Party spokesperson said: "Jeremy has today spoken to a number of colleagues in the Parliamentary Labour Party and will continue to do so throughout the day. He has begun the process of appointing a new front bench team."