Duncan, who has been strongly linked to the vacant chief executive post at ITV, has said that the move could lead to unfair cooperation between the two companies and has called on regulator Ofcom to review the situation.
"It would be helpful to know Ofcom and the government were looking at it properly," he said at a meeting of the Broadcasting Press Guild yesterday. "It is important that [ITV and Sky] are effectively standalone businesses."
His comments come on the back of reports yesterday that Sir Richard Branson again vociferously opposed the Murdoch empire's growing media dominance, describing it as a threat to democracy in the UK.
Duncan said he was concerned how the ITV/Sky relationship would affect ITV operationally.
One area he singled out was ITV's multi-channel strategy, the foundation of which is built on Freeview, the free digital TV service that is a direct rival to Sky. ITV has launched three free-to-air digital channels in ITV2, ITV3 and most recently ITV4.
Duncan is concerned that the Sky relationship could compromise that strategy. ITV has also been in talks with the BBC about launching a free satellite TV service, which again would compete directly with Sky.
"What is ITV's corporate line on Freesat?" he asked.
James Murdoch, BSkyB chief executive, defended his firm's £940m swoop on ITV as the behaviour of a "supportive and long-term shareholder of ITV".
However, many leaders in the media industry interpret the acquisition as a means for Sky to oppose takeover bids for ITV, such as NTL's attempts to buy the broadcaster.
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