Sony BMG has suffered its first defections since a dispute between the music company's two shareholders prompted a management shake-up in February.

Don Ienner and Michelle Anthony, the two most senior executives at its Sony Music Label Group, have resigned with immediate effect.

Industry members familiar with the situation said their resignations were related to the decision this spring to replace Andy Lack, the Sony-appointed chief executive, with his Bertelsmann-backed counterpart, Rolf Schmidt-Holz.

Ms Anthony, a former lawyer and one of the most powerful women in the music business, and Mr Ienner, who has worked with artists ranging from Bob Dylan to Franz Ferdinand, were in charge of labels including Columbia Records, Epic, Sony Music Nashville and Sony's urban music division.

It was not clear on Thursday night whether the two had found jobs with one of the three other largest music companies, although it was not thought that EMI or Warner Music had recruited the pair.

Mr Ienner was chairman and chief executive of the division, and Ms Anthony president and chief operating officer.

Their departures led to the promotion of Rob Stringer, current head of the Sony Music Label Group in the UK and Ireland. Mr Stringer, who has worked with artists including George Michael, will become the group's president in September 1. Until then, the business will report to Tim Bowen, Sony BMG's chief operating officer.

Mr Schmidt-Holtz said: "Donnie and Michelle have been the bedrock upon which Sony Music's success has been built over the last 18 years and we are very appreciative of their important contributions during this period."

He added: "Rob has been with Sony Music throughout his 20-year career and now is the perfect time for him to take on this senior role."

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