This morning’s ruling decided the newspaper was guilty of libel but left the level of damages awarded to Mr McKenna to be set at a further hearing in October.

Mr McKenna, whose self-help business has an annual turnover of £2.5 million, accused the newspaper of turning him into a "laughing stock" after printing articles accusing him of buying a degree from an American university.

He said that he was "pilloried" by Daily Mirror journalist Victor Lewis-Smith from 1997 onwards and was devastated by another mention of his "bogus degree" from La Salle University, Louisiana, in an October 2003 article in The Mirror.

In it, Mr Lewis-Smith, wrote: "I discovered that anyone could be fully doctored by La Salle within months (no previous qualifications needed), just so long as they could answer the following question correctly: do you have $2,615?".

The newspaper’s publishers, who denied libel, called evidence from Mr Lewis-Smith’s co-writer, Paul Sparks, who said that he was told by La Salle that he could obtain a doctorate for that fee within a matter of months and without undertaking any formal course.

Mr Justice Eady, who heard the case without a jury, said today that he could not accept that the newspaper had discharged the burden of proving that the sting of the words complained of was substantially true.

The court heard how La Salle University was not a properly accredited academic institution, but the judge decided that Mr McKenna enrolled on and completed his academic course in good faith and could not have been aware of this.

"Mr McKenna was not, in my judgment, dishonest and, for that matter, whatever one may think of the academic quality of his work, or of the degree granted by La Salle, it would not be accurate to describe it as "bogus," the judge said.

Mr McKenna told Sky News: "The university was tarnished but I did not just hand over a cheque and get a degree. I did the work for it.

"The claim was that I bought the degree and hadn’t done any work, that I knew it was a fraudulent degree and I did it to deceive the public. These are serious allegations. I wrote to the newspaper and asked them to withdraw the allegations. Instead they republished them again and again and again.

"Eventually, reluctantly, I had to take legal action to stop them because it was damaging my reputation and essentially hurting people I employed as well."

The judge ordered The Mirror to pay Mr McKenna's costs, which he said were "no doubt massive."

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