Pop Idol judge Simon Cowell is being sued for allegedly stealing the idea for a new reality TV show.
Simon Cowell is backing the new show, but will not present it
Last month, Cowell and the ABC network announced plans for The Million Dollar Idea, which will reward contestants who come up with the best business schemes.
Roaring Entertainment, the creators of an existing show called Million Dollar Idea, said it was a "patent rip-off".
Cowell's spokesman Max Clifford said: "It's very different in lots of different ways. It's an original idea."
Roaring Entertainment said Million Dollar Idea began in 2003 and is now syndicated to 125 stations across the US.
It allows budding inventors and entrepreneurs to pitch their ideas to experts, with the most promising proposals winning services worth $50,000 (£28,000) to develop their products.
In the ABC show, contestants' ideas will be judged by a panel of three business leaders, dubbed The Millionaires.
Nine hopefuls will get $50,000 each and go through to the final, where the winner will be given $1m (£555,000).
Cowell will not present the show because of his American Idol contract with Fox TV.
Mr Clifford said the name of the ABC show would be changed and The Million Dollar Idea was "only ever a working title".
He also said the show format was devised by businessman Peter Jones, who appeared as a judge on BBC series Dragon's Den.
"ABC were interested in taking Dragon's Den but they didn't want any of the other judges," Mr Clifford said.
"I introduced Peter to Simon, and Peter had what I thought was a very good idea for a programme - which we both thought would do well in the States."
Cowell and ABC both added their input to the format, he said.
"[With] just about every programme that comes out, you get someone saying 'this was my idea'. It's a fact of life," Mr Clifford said. "I refute any of these charges."
ABC and production company FremantleMedia North America, which is also named in the legal action, were unavailable for comment.
Roaring Entertainment's legal papers said: "While imitation may be the sincerest form of flattery, imitation in the form of outright copying is not flattery at all - it is intellectual property theft."
The company and Million Dollar Idea's creators and hosts Jean Golden and Todd Walker say they offered the show to ABC in early 2004.
They filed the legal case in Los Angeles and are seeking unspecified damages.