And patents enjoy protection only under civil law: a patent-holder who believes their idea has been ripped off must themselves sue for compensation through the civil courts.
"If I was to nick your car, which is worth £10,000, say, I could go to jail," Trevor Baylis told the BBC.
"But if I were to nick your patent, which is worth a million pounds, you'd have to sue me.
"And if I was a colossal company, or indeed another country, that had stolen your invention, how could you find a million pounds a day to take me to court?"
The answer, he says, is to make stealing a patent a criminal offence - just as it's already a criminal offence to steal copyright from creative people like authors and musicians.
That way the state, not the individual inventor, would bear the costs of going to court.
"I believe that theft of intellectual property rights should be treated as a white collar crime," he says in a letter to Business Secretary Lord Mandelson.
"I believe that UK plc should stand behind those courageous individuals whose ideas can change all our lives both commercially and socially."
Honest, decent people running reputable businesses infringe patents. They might not know the patent exists, or their patent attorney might have told them it was invalid or not infringed
Member of Chartered Institute of Patent Attorneys
Mr Baylis, who lives in an eccentric house-cum-workshop which he built himself on Eel Pie Island, in the middle of the River Thames off Twickenham, says he has the support of the Federation of Small Businesses, the Institution of Mechanical Engineers and of his local MP, the Liberal Democrat Treasury spokesman Vince Cable.
In 2002 Mr Cable introduced a private member's bill which increased the penalties for copyright theft from a maximum of two years to 10 years imprisonment.
Mr Cable told BBC News: "There isn't the protection that exists in other areas of intellectual property.
"If people steal ideas from creative artists, you can go to prison for that. But patent theft is just part of life."
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But the defenders of the present system say changing the law may not be the right answer.
Patents can be extremely complex things and the criminal law is simply too blunt an instrument to use when disputes arise.
Peter Jackson is a fellow of the Chartered Institute of Patent Attorneys.
"First of all you've got to decide whether the patent covers the thing properly", he says.
"And having done that you've got to decide whether what the alleged infringer is up to falls within that strict wording.
"That can take days and weeks and months of deliberation by highly skilled lawyers, and I'm not sure the criminal system is well-suited to that kind of action."
Other members of the institute are more forthright.
One calls the idea of criminalising patent infringement "barking mad".
Another says the parallel with copyright protection is not as close as it might appear: "Patent infringement is not remotely like flogging knock-off CDs.
"Honest, decent people running reputable businesses infringe patents. They might not know the patent exists, or their patent attorney might have told them it was invalid or not infringed."
And patent attorneys say criminalisation might have a "chilling" effect on innovation, by forcing a patent-holder's rivals to "play safe" for fear of committing a criminal offence.
Instead they point to the mediation service run by the Intellectual Property Office as an alternative to costly legal action.
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