Chief executive Mr Duncan, who is quitting after five years at C4, said advertising regulation was still stuck in pre-internet days.
He told TV movers and shakers at the Royal Television Society's Cambridge Convention: "This is a massively over-regulated industry, especially in the advertising area. It is barmy, it's absolutely barmy."
He continued: "The TV broadcaster is stuck in a system based on 20, 30 years ago, when all the advertising (money) was on television and there weren't any competitors. The internet has to be thought about alongside television.
"The change we're going through is going to accelerate and we have a regulatory policy and a debating cycle which is years behind."
He warned: "If I have one big point to make, it is that this whole industry I think is in denial about the scale of change that is coming.
"And if we don't get de-regulation, more freedom around advertising, the internet companies, the West Coast and America, will suck more and more money out of British content, and we'll end up with a weaker system.
"And it's a really big problem."
Mr Duncan joined Mark Thompson, director-general of the BBC, ITV executive chairman Michael Grade and Dawn Airey, chair and chief executive of Five, to discuss the major issues facing broadcasters as the convention wound up today.
Mr Grade echoed Mr Duncan's view that potential revenue from UK content could end up in the US.
He hit out at the Competition Commission's decision to block Project Kangaroo, a plan by BBC Worldwide, ITV and Channel 4 to launch an on-demand video service.
He said that because of that decision "much of the money that our content would generate will end up in America".
He added: "What we need now is decisions. There is a point now where any decision is a good decision, we just need the decision.
"Every time someone comes up with a brilliant idea we go into another round of consultations, by which time there's an election, there's a whole new lot in, and we start all over again."
Culture Secretary Ben Bradshaw has said he wants to change the Government's approach to product placement, allowing it on television for the first time.
Ministers hope lifting the ban will throw a lifeline to struggling independent broadcasters such as ITV by opening new multimillion-pound revenue streams.
Ofcom's chief executive Ed Richards said the Government's decision to examine the issue of product placement opened up the way for Ofcom to look at sponsorship "so there's quite a significant opportunity there".
Much of the conference has been dominated by a fiery debate prompted by Mr Bradshaw's calls for the BBC Trust to be scrapped and the corporation to stop expanding.
Mr Bradshaw gave a keynote speech at the RTS event on Wednesday and afterwards became embroiled in a heated exchange with BBC Trust chairman Sir Michael Lyons.
Yesterday, Mr Thompson hit back at Mr Bradshaw's questioning of the Trust as both "cheerleader" and regulator.
Mr Thompson said: "The people Ben should ask this question of is those colleagues of his in the present cabinet who invented the BBC Trust, approved it and enshrined it in a charter which still has well over seven more years to run."
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules hereComments are closed on this article