Banker Nathaniel Rothschild has lost his appeal over a newspaper story which he said portrayed him as a "puppet-master" who brought together Lord Mandelson and Russian oligarch Oleg Deripaska.
The 41-year-old Swiss-based financier challenged a February 2012 ruling by Mr Justice Tugendhat that Associated Newspapers had established that the meaning of the May 2010 article in the Daily Mail was substantially true, despite admitted inaccuracies.
The newspaper's case was that Mr Rothschild took Lord Mandelson, then European Commissioner for Trade, on a January 2005 trip to Siberia in order to impress Mr Deripaska, when he knew, or ought to have known, that if anyone found out about it, Lord Mandelson would have been compromised.
The judge, at London's High Court, dismissed the claim for substantial libel damages, saying he accepted the newspaper's submission that Mr Rothschild's conduct was inappropriate in a number of respects.
Mr Rothschild's evidence was that the presence of Lord Mandelson on the overnight trip to Abakan with himself, another friend - Sebastian Taylor, Peter Munk - chairman of Barrick Gold, and Mr Deripaska, who had a chalet nearby, was "purely social".
Lord Mandelson and Mr Deripaska were not parties to the action and did not take any part in the trial.
It was emphasised that the case was not about them and the newspaper made no allegations they had done anything wrong.
Dismissing the appeal, Lord Justice Laws, Lord Justice McCombe and Sir David Eady said they were satisfied that Mr Justice Tugendhat reached the correct conclusion.