Gerry Ryan has been left reeling after a shake-up of his production team.
As part of a dramatic overhaul, 2FM chief John McMahon has moved Gerry's resident producer Siobhan Hough to the early morning slot.
Hough, who has been a staff member with RTE for more than 20 years, is now working as head producer of The Colm and Jim Jim Breakfast Show.
RTE veteran Alice O'Sullivan has returned to her roots as head producer of the Gerry Ryan Show.
The unexpected move is said to have caused tension behind the scenes, with staff on both programmes struggling to adapt to the change.
"Everyone, including Gerry himself, was absolutely stunned by the news that Siobhan would be leaving the show," said a programme insider.
"She's been with him from day one and was considered by everyone to be his right-hand woman. They've been working together since the early Eighties when Siobhan worked on his night-time show.
"When Gerry moved to a day-time slot in 1988, Siobhan moved with him working first as a researcher, then a producer and eventually being promoted to head producer of the Gerry Ryan Show.
"Naturally he was disappointed to see her go to another show after all those years but he had no say in the matter," they added.
The star declined to comment on the issue.
A representative for RTE radio claimed there was no ill-feeling over the decision.
"Siobhan Hough and Alice O'Sullivan are two of RTE Radio's most esteemed producers," said the spokesperson.
"Both work closely together every day, with both shows overlapping each morning, and both producers are firmly focused on increasing audience for 2fm in the mornings."
The spokesperson added that, under common practice in RTE Radio, producers, researchers and producers-in-charge were reassigned to new programmes, following extensive changes to the 2fm schedule in January 2010.
"This is standard procedure and is the mechanism by which shows and teams are kept fresh, inventive and engaged with the audience," they added.
Despite working on a different radio show this year, Siobhan has continued to work with Gerry on the production of his RTE television show, Operation Transformation.