Strictly Come Dancing's Brian Fortuna has announced he is leaving the show after changes were made to the format.
The American said he had decided to quit after he and some colleagues were asked to concentrate on professional-only routines in this autumn's series, rather than dancing with celebrities.
The number of celebrity dancers is to be cut this year from 16 to 14.
A BBC spokeswoman said: "We would like to thank [Brian] for all his hard work over the last two series."
The BBC has recruited three new male dancers for the 2010 series and asked five of its regular professionals - including 2009 semi-finalist Fortuna - to give up their usual mentoring role.
The show's producers wanted Fortuna, along with Ian Waite, Matthew Cutler and husband and wife Darren Bennett and Lilia Kopylova, to form a new professional group which would perform "show-stopping dance spectacles" each week.
But Fortuna said on Tuesday night that he had chosen to leave Strictly and concentrate instead on the West End stage show Burn The Floor, which will see him perform with his 2009 Strictly partner, actress Ali Bastian.
"I really enjoyed working on Strictly over the years - loved the fans and loved all the people I got work with - but there are changes planned for the next season so I've decided not to return to the show," he said.
"Both Ali and I are looking forward to seeing all our fans at the Shaftesbury Theatre."
Fortuna joined Strictly in 2008 when he partnered M People singer Heather Small.
He and Bastian began dating during their time on the show.
High School Musical
The BBC said the three new male professionals would each bring their own area of dance expertise.
Robin Windsor has been touring with Burn The Floor, a show he helped to choreograph.
Jared Murillo was a principal dancer in the first two High School Musical movies, while Artem Chigvintsev is a Latin champion and graduate of the US version of Strictly, So You Think You Can Dance.
BBC controller of entertainment commissioning Mark Linsey said: "I'm delighted to be welcoming three new, fantastic dancers to Strictly and am really excited about the introduction of a professional dance group, giving us even more opportunities to feature different areas of expertise and more genres of dance than in any other series."
The changes come a year after Strictly was embroiled in a row over alleged ageism when producers replaced veteran choreographer Arlene Phillips with former winner Alesha Dixon on the judging panel.