An article suggesting that Sir James Dyson was a hypocrite who "screwed" the country damaged his reputation, the High Court has heard.
The entrepreneur is suing Mirror Group Newspapers (MGN) for libel over an article published in January 2022.
Mr Dyson told court the article was "a personal attack on all that I have done and achieved in my lifetime and is highly distressing and hurtful".
MGN is defending the claim, including on the basis of honest opinion.
In the article, journalist Brian Reade referred to Mr Dyson, who has a factory base in Malmesbury, as "the vacuum cleaner tycoon who championed Vote Leave due to the economic opportunities it would bring to British industry before moving his global head office to Singapore".
He continued: "Kids, talk the talk but then screw your country and if anyone complains, tell them to suck it up."
'Vicious and vitriolic'
Sir James, 76, sat in front of his lawyers in the courtroom in the Royal Courts of Justice during the first day of the trial on Tuesday.
In a witness statement, the inventor, who backed the UK leaving the European Union, also said that a decision to establish a Dyson global headquarters in Singapore "had nothing to do with Brexit at all".
Justin Rushbrooke, counsel for the inventor, told the court the article was a "highly vitriolic piece of journalism" with no evidence to justify its critical claims.
He added that an "honest opinion is supposed to give latitude but it is not a licence for a journalist to mislead the reader."
In a statement, a Dyson spokesperson said Sir James had brought the legal claim "as a last resort".
The spokesperson continued: "The Mirror Group Newspapers has admitted to the Court that Sir James is recognised as one of the UK's greatest ever inventors and business leaders and that he is one of the UK's leading philanthropists, particularly in the educational fields, yet the allegations made by the newspaper in its article were vicious, vitriolic and attacked his personal character in the very worst way."
However, Adrienne Page, counsel for MGN, said in written submissions that Sir James' approach to the legal claim "has been markedly unreasonable, wholly disproportionate and abusive".
She continued in written submissions: "It might strike the court as surprising that a person who enjoys a level of success and influence as this claimant would choose to spend somewhere in the region of £1m litigating to trial the question of whether these short passages represent an opinion an honest person could have held."
The trial before Mr Justice Jay is set to conclude on Friday with a decision expected at a later date.