The former Conservative party co-treasurer has won £180,000 libel damages after he successfully sued the Sunday Times over allegations about charging fees to meet David Cameron.
The High Court in London also ordered the paper to pay £500,000 in costs after it falsely claimed Peter Cruddas was charging £250,000 for opportunities to meet the Prime Minister.
Cruddas, 59, brought the claim against Times Newspapers Ltd and two members of the newspaper's Insight team over three articles which appeared in March 2012.
The articles appeared after journalists from the Insight investigations team, Heidi Blake and Jonathan Calvert, pretended to be agents for foreign investors who wanted to explore making donations to the party and hired a lobbyist, through whom they arranged to meet Mr Cruddas.
Unknown to him, each reporter carried a concealed camera with an audio recording facility.
The articles claimed he corruptly offered people the chance to gain an unfair advantage and influence government policy via secret meetings with Cameron.
Cruddas resigned from his role after reports appeared in the newspaper.
Following the ruling, Cruddas said a "dark cloud" has been lifted from him.
He added: "My world was turned upside down when that article was published. I remember vividly having to walk into my offices the day after the article was published and face 500 of my staff, many of whom had a clip of the Sunday Times interview on their video screens. It was humiliating.
"I was also embarrassed to accept invites to events, which meant that my charities suffered. The Conservative Party cut me off within two hours of the story breaking and did not want to hear my side of the story.
"I was constructively dismissed from my role as party treasurer and made to feel like an outcast as the Prime Minister and the party lined up to criticise me on television and radio. This hurt me immensely and further damaged my reputation.
"Today is a good day for me. I am delighted that my good name has been restored. My family, friends and legal team have shown me huge support throughout, which has kept me going, and I sincerely thank them."
Jeremy Clarke-Williams, who represented Cruddas, said: "This is a devastating and unequivocal judgment which provides the clear vindication Mr Cruddas deserves.
"We are delighted that his reputation as a successful and honest businessman and generous philanthropist has been restored."
Cameron Humiliated Cruddas
Former Conservative treasurer and major donor Lord Ashcroft said the party "needs to learn major lessons from this debacle".
Writing on the ConservativeHome website, Lord Ashcroft said: : "I hope that Mr Cameron will now offer Mr Cruddas an apology for his criticism of him, and for forcing him to step down as treasurer with such haste when Mr Cruddas was fulfilling his unpaid role well and effectively. That would be the right thing to do."
Conservative chairman Grant Shapps repeatedly refused to apologise on behalf of the party for the way Mr Cruddas was treated.
In his judgment, Mr Justice Tugendhat said that Mr Cruddas had been subjected to a "massive public humiliation" by the Prime Minister, when Mr Cameron said in a speech in the wake of the Sunday Times report that what he said was "completely unacceptable and wrong".
"The Prime Minister did not know what Mr Cruddas had said. All he knew was what The Sunday Times had reported. This speech by the Prime Minister was a massive public humiliation for Mr Cruddas," said the judge in his finding.
Journalists' Glee at Getting Cruddas
In his finding on malice, the judge said that Mr Calvert and Ms Blake did know that the articles were false in the meanings which they knew them to bear.
They had "a dominant intention to injure Mr Cruddas, and they expressed delight when they learnt that they had caused his resignation".
He said the allegations, which went to Mr Cruddas's personal honour and integrity, received the maximum possible publicity and were very grave.
"Mr Cruddas has suffered great personal distress, both directly, and though his family and the employees of his company.
"He has suffered public humiliation from the Prime Minister.
"He had a high standing in society, both for his business success and his charitable work, all of it earned by him personally through his own efforts, and from a disadvantaged start.
"The conduct of the defendants in contesting the action both before and at the trial has been offensive."
The judge said the only claimant in the action was Mr Cruddas, although a number of other people were named in the judgment, including the Prime Minister and the Chancellor.