Lundie, who spent more than three years at Oxfam, previously worked at Save the Children as director of brand and communications between 2010 and 2014.
He rejoined the charity today (7 August) as centenary director, his LinkedIn profile states. According to a job ad posted earlier this year, "the centenary director will be responsible for leading the design, implementation and coordination of Save the Children's global centenary plan in 2019".
Before joining Save the Children in 2010, Lundie was senior development producer at the BBC between 2008 and 2010. Prior to that, he was deputy editor for children's television programme Blue Peter.
Lundie's replacement, Matthew Sherrington, has been appointed in an interim capacity for six months. He starts in the role today.
A spokeswoman for Oxfam said: "After Jack announced his departure, Oxfam made the decision to appoint an interim director while we review the scope of the role in order to make it as effective as possible, and complete the formal recruitment process to find the next permanent director.
"Matthew has already spent a week shadowing Jack and will lead on key engagement opportunities such as Oxfam's 75th anniversary in October and the World Economic Forum in Davos in January."
Before joining Oxfam, Sherrington was an independent consultant, providing strategic consultancy to charities. Prior to this he was joint managing director at The Good Agency between 2010 and 2013. He has been a columnist at PRWeek sister title Third Sector.
PRWeek has contacted Lundie and Save the Children for comment.