Bridgepoint Capital has denied it is looking to sell its stake in Opus.
Sources said that the venture capitalist was looking to exit the investment and had put Opus on the market.
But a Bridgepoint spokesman said: "There are no plans currently for Bridgepoint to withdraw its stake in Opus."
Bridgepoint first invested in Opus in 1998, when the company underwent amanagement buy-out.
Bridgepoint owns 72% of the company, with 26% held by Opus management and the remaining 2% owned by the Royal Bank of Scotland.
Opus chief executive Ian Brice said: "Bridgepoint has absolutely no plans to withdraw its shareholdings in Opus.
"Opus continues to adopt its growth strategy and these plans remain unaltered."