Scotland's new cultural commission has been attempting to save face following the resignation of one of its members after just two days in the job.
Mr Armstrong was critical of the treatment of Scottish Opera
Composer Craig Armstrong said he was unaware when he was appointed that he was the only practising artist on the eight-strong commission.
He also condemned plans to scale down Scottish Opera.
The culture commission, headed by James Boyle, is tasked with finding some radical solutions to arts funding.
Mr Armstrong, 45, from Glasgow, said that as the only practising artist on the commission he felt unable to accept the post.
He also condemned the plans to scale down Scottish Opera and said he believed it was not too late to reverse the decision to axe almost half its workforce.
He said: "Contrary to what I hoped, the commission does not contain practising artists in suffient proportion from varied artistic and cultural backgrounds.
Craig Armstrong has been acclaimed for film soundtracks
"With respect to the other commissioners, I believe this lack of representation could undermine the commission at a difficult time for the arts in Scotland."
The other commission board members are George Black, chief executive of Glasgow City Council; Lucy Mason, chief executive of Dance Base; Gordon Jeyes, director of children's services at Stirling Council; Brian Lang, principal at St Andrews University; Shonaig Macpherson, president of the Edinburgh Chamber of Commerce and Enterprise; Colin Marr, Eden Court Theatre director, and Ian Ritchie, a director of the Edinburgh International Film Festival.
Mr Boyle, the former head of the Scottish Arts Council, will lead the commission, which will sit for 12 months before making recommendations to Scottish ministers.
Mr Armstrong, who grew up in the Shettleston area of Glasgow, has won a clutch of international awards including a Golden Globe for the score of Baz Luhrmann's Moulin Rouge and a Bafta for Romeo and Juliet.
He has found critical sucess with other film soundtracks such as The Quiet American and The Magdelene Sisters and his solo album The Space Between Us was a worldwide hit.