The MP for Stockton North, Alex Cunningham, has been appointed as shadow pensions minister.
The former journalist, who was elected to parliament in May 2010, made the announcement on Twitter on 13 October.
He tweeted: "Delighted [to] accept @Debbie_Abrahams' invitation [to] join shadow work and pensions team as shadow pensions minister. Tories in a right mess on it."
The position has been vacant since July, when former shadow pensions minister Angela Rayner was promoted to shadow minister for education and shadow minister for women and equalities, after a series of cabinet resignations.
Embattled Labour leader Jeremy Corbyn had struggled to fill the position while awaiting the results of his second leadership contest, which he comfortably won last month.
Cunningham was previously shadow minister for the natural environment before he also resigned from the position in the wake of the vote to leave the European Union (EU). He criticised Corbyn's perceived lack of campaigning to remain in the EU during the build-up to the referendum.
Also writing on Twitter, Rayner welcomed Cunningham to the role.
She wrote: "Congratulations to my colleague @ACunninghamMP on becoming shadow pensions minister."
Cunningham was also a member of the Work and Pensions Committee between November 2010 and June 2011.
He has previously expressed support for the Women Against State Pension Inequality (WASPI) campaign, claiming "it will be the poorest women who suffer the most as a result of the government's plans, those who do not have savings to fall back on and are in low-paid jobs."
The government has confirmed the current interim chairwoman of The Pensions Ombudsman (TPO), Caroline Rookes, will continue the role in a permanent capacity.
The Pensions Management Institute (PMI) has appointed three non-executive directors and an executive director to its board.
Former Financial Regulators Complaints Commissioner Antony Townsend is to become chair of an expanded Determinations Panel at The Pensions Regulator (TPR).
Six members of Ross Trustees’ pension trustee and support teams have been promoted into new roles.