The Attorney General, Lord Goldsmith, has failed in a legal bid to stop publication of fresh information surrounding the cash-for-honours investigation.
A judge refused to grant an injunction to stop The Guardian printing a story suggesting Lord Levy may have attempted to influence the evidence of senior Downing Street aide Ruth Turner.
Lord Goldsmith secured an injunction on Friday blocking the BBC from running a news item which the police had said could "impede their inquiries".
Its terms were later relaxed to allow the BBC to report that Ms Turner was the author of the document and that it concerned Tony Blair's chief fund-raiser.
But The Guardian has gone further, suggesting detectives were examining whether Lord Levy had attempted to "shape" her evidence to the inquiry.
The paper claimed detectives were investigating a meeting between Ms Turner and Lord Levy last year, an account of which the Downing Street aide gave to her lawyers and which has been given to police.
In a joint statement, the Attorney General's office and Scotland Yard said: "We were made aware late yesterday evening that the Guardian newspaper was planning to run an article which gave us cause for concern.
"We sought to obtain an undertaking from them that they would not run aspects of the story. They refused so we sought an injunction which was refused on the grounds that the newspaper had already been printed."
Lawyers acting for the newspaper argued such a move would be "highly unusual" when no charges had been brought.
In a statement on its website, the paper said: "The judge said the case was finely balanced but she refused to accede to the Attorney's request, saying that the story was already in the public domain because it was already being printed."