Lord Ashcroft has had a complaint against BBC Radio 4's Today programme rejected by Ofcom.
Lawyers for the Tory peer said the show suggested he had been accused of tax evasion during Prime Minister's Question Time last year.
He claimed he had been denied a right of reply to "criminal" allegations.
Ofcom ruled that the breakfast news programme had showed "no unfairness" in its coverage.
The media watchdog said that the report, broadcast last December, made it clear that, while Liberal Democrat MPs had initially raised a question about tax evasion, they had not accused Lord Ashcroft of this.
It added that the report did not amount to an allegation of wrongdoing, so did not require a response.
Lord Ashcroft felt he did not have a chance to point out that the Today programme's introduction to the day's parliamentary proceedings had confused tax evasion with tax avoidance.
The item was introduced with the words: "The Liberal Democrats have targeted the Conservative Party donor and deputy chair Lord Ashcroft in a row about tax evasion.
"The Liberal Democrat deputy leader Vince Cable used parliamentary privilege to name the peer as a non-dom, accusing him of not paying tax in the UK on overseas earnings."
The BBC said it did not accept that the passage made the allegation claimed by the complainant.
It explained that this was an introduction to the report, which chiefly covered an exchange between Harriet Harman and Vince Cable.
It added that the item contained interruptions from members of parliament mentioning Lord Ashcroft's name in connection with the debate, but did not imply an accusation of tax evasion.
The BBC concluded that the report used "neutral, factual reporting".
But Ofcom did acknowledge that the opening sentence of the report may have led some listeners to believe that Dr Cable had accused Lord Ashcroft of tax evasion.
It then added that the relevant parts of parliamentary dialogue had subsequently been included in the remainder of the item.
The watchdog said that the report as a whole made it clear that Lord Ashcroft had been accused of tax avoidance, which in itself is not a criminal matter.